Language：English   Publishing type：Research paper (scientific journal)  

Time-correlated Single Ion Counting Mass Spectrometer with Long and Short Time-of-flight Tubes and an Evaluation of its Performance for Use in Trace Analysis of Allergenic Substances

Language：English   Publishing type：Research paper (scientific journal)  

Resonant and non-resonant femtosecond ionization mass spectrometry of organochlorine pesticides

Repository Public URL： http://hdl.handle.net/2324/2794914

Language：English   Publishing type：Research paper (scientific journal)  

Determination of nerve agent metabolites in human urine by femtosecond laser ionization mass spectrometry using 2-(bromomethyl)naphthalene as a derivatizing reagent

DOI： 10.1016/j.aca.2019.04.0120

Repository Public URL： http://hdl.handle.net/2324/2800475

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.optlastec.2017.12.016

Language：English   Publishing type：Research paper (scientific journal)  

A two-color pump beam (800 and 1200 nm) was introduced into hydrogen for molecular phase modulation, and a probe beam (267 nm) to generate Raman sidebands, by coherent frequency modulation based on four-wave Raman mixing. The phase and temporal profile were evaluated by means of a self-diffraction frequency resolved optical gating (SD FROG) system. The relative phases among the Raman sidebands were controlled by changing the angle of a thin CaF2-plate inserted into the 267-nm beam path, suggesting that a train of 2.6-fs pulses was generated in the deep-ultraviolet region.

DOI： 10.3390/app8050784

Language：English   Publishing type：Research paper (scientific journal)  

A standard sample mixture containing 51 pesticides was separated by gas chromatography (GC), and the constituents were identified by mass spectrometry (MS) using femtosecond lasers emitting at 267, 400, and 800 nm as the ionization source. A two-dimensional display of the GC/MS was successfully used for the determination of these compounds. A molecular ion was observed for 38 of the compounds at 267 nm and for 30 of the compounds at 800 nm, in contrast to 27 among 50 compounds when electron ionization was used. These results suggest that the ultraviolet laser is superior to the near-infrared laser for molecular weight determinations and for a more reliable analysis of these compounds. In order to study the conditions for optimal ionization, the experimental data were examined using the spectral properties (i.e., the excitation and ionization energies and absorption spectra for the neutral and ionized species) obtained by quantum chemical calculations. A few molecules remained unexplained by the currently reported rules, requiring additional rules for developing a full understanding of the femtosecond ionization process. The pesticides in the homogenized matrix obtained from kabosu (citrus sphaerocarpa) were measured using lasers emitting at 267 and 800 nm. The pesticides were clearly separated and measured on the two-dimensional display, especially for the data measured at 267 nm, suggesting that this technique would have potential for use in the practical trace analysis of the pesticides in the environment.

DOI： 10.1021/acs.analchem.8b00537

Language：English   Publishing type：Research paper (scientific journal)  

The ionization and fragmentation processes were examined for a standard sample mixture containing 16 polycyclic aromatic hydrocarbons (PAHs) and 3 nitro-PAHs (NPAHs) by gas chromatography combined with mass spectrometry (GC/MS) using a femtosecond laser emitting at 400, 800, or 1200 nm as the ionization source. The signal intensities of NPAHs were lower and the fragmentation more extensive compared to those values for PAHs, especially at shorter wavelengths (400 nm). These results can be explained by efficient intersystem crossing to triplet levels and the shorter excited-state lifetimes of neutral NPAHs molecules, compared to the pulse width of the laser. Fragmentation was significantly suppressed by nonresonant multiphoton ionization when a laser emitting at longer wavelengths (1200 nm) was used. This result can be explained by the absorption spectrum of the molecular ion and the excess energy remaining in the ionized state. In fact, there was no absorption band at 1200 nm for the molecular ion, and the excess energy would be minimal when a near-infrared laser is used, which suppresses the fragmentation even for NPAHs. A doubly charged molecular ion was observed for PAHs but not for NPAHs, probably owing to the higher stability of the PAH molecule, the electrons of which are more strongly bound and are more resistive to field ionization. To demonstrate the utility of this technique, the sample extracted from particulate matter 2.5 (PM2.5) emitted from a diesel engine was measured. NPAHs as well as PAHs were clearly determined at 1200 nm, at which the background signal arising from the interference was drastically suppressed.

DOI： 10.1021/acs.analchem.8b00125

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A sample containing nitrated aromatic hydrocarbons (NPAHs) was injected into the sample inlet port of a gas chromatograph (GC), along with hydrazine, a reducing reagent. The analytes that eluted from the GC column were measured by mass spectrometry (MS) using an ultraviolet femtosecond laser as the ionization source. When no reducing reagent was used, large numbers of polycyclic aromatic hydrocarbons (PAHs) including NPAHs were observed in the two-dimensional GC/MS display. In contrast, when hydrazine was present, reduced forms of NPAHs, which included amino PAHs, were detected. When a palladium or platinum catalyst was placed in the GC inlet port, the compounds were further reduced to non-aromatic hydrocarbons. The present approach would be useful for studies to evaluate the chemical reaction that converts the constituents contained in exhaust emitted from a diesel engine. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2017.09.049

Language：English   Publishing type：Research paper (scientific journal)  

The ionization and fragmentation processes for pentachlorobenzene were examined using a femto-second laser emitting at 400, 800, and 1200 nm. A molecular ion was clearly observed in the mass spectrum, since the molecule can be directly ionized from the singlet electronic exited state before relaxation to triplet levels, because the pulse width of the laser is shorter than the lifetime of the excited state. Fragmentation was minimal at 1200 nm, in contrast to ionization at 800 and 400 nm. Indeed, a doubly-charged molecular ion was prominent at 800 nm, owing to the absorption band of the singly-charged molecular ion at this wavelength. Fragmentation was further enhanced at 400 nm, which can be explained by the dissociation of the doubly-charged molecular ion having a larger absorption band at 400 nm. Fragmentation was strongly affected by the absorption character of the ionic species, i.e., singly and doubly-charged molecular ions, appeared in the process of multiphoton ionization.

DOI： 10.1039/c7an01172e

Language：English   Publishing type：Research paper (scientific journal)  

In 2001, a concept was proposed to generate mode-locked ultrashort laser pulses with a repetition rate in excess of 10 THz [Phys. Rev. Lett. 87, 223901 (2001)], which has not been demonstrated so far. In the present research, the concept is experimentally demonstrated using a dispersion-compensated high-finesse cavity filled with hydrogen gas. Second-order intensity autocorrelation is used for distinguishing two cases with and without mode-locking as well as for characterization of the temporal profile. Mode-locked sub-30-fs pulses with a repetition rate of 17.6 THz are synthesized by continuous-wave laser lines generated via stimulated Raman scattering and four-wave Raman mixing induced in the high-finesse cavity. (C) 2017 Optical Society of America

DOI： 10.1364/AO.56.007636

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Nerve agent metabolites, i.e., isopropyl methylphosphonic acid (IMPA) and pinacolyl methylphosphonic acid (PMPA), were derivatized by reacting them with 2,3,4,5,6-pentafluorobenzyl bromide (PFBBr) and were determined by mass spectrometry using an ultraviolet femtosecond laser emitting at 267 and 200 nm as the ionization source. The analytes of the derivatized compounds, i.e., IMPA-PFB and PMPA-PFB, contain a large side-chain, and molecular ions are very weak or absent in electron ionization mass spectrometry. The use of ultraviolet femtosecond laser ionization mass spectrometry, however, resulted in the formation of a molecular ion, even for compounds such as these that contain a highly bulky functional group. The signal intensity was larger at 200 nm due to resonance-enhanced two-photon ionization. In contrast, fragmentation was suppressed at 267 nm (nonresonant two-photon ionization) especially for PMPA-PFB, thus resulting in a lower background signal. This favorable result can be explained by the small excess energy in ionization at 267 nm and by the low-frequency vibrational mode of a bulky trimethylpropyl group in PMPA.

DOI： 10.1021/acs.analchem.7b00386

Language：English   Publishing type：Research paper (scientific journal)  

A technique involving cross-correlation frequency-resolved optical gating is applied in characterizing an optical pulse train consisting of several spectral components. An optical beat was used as a reference pulse for measuring the relative spectral phase among the spectral components in the test pulse generated by four-wave Raman mixing in hydrogen gas. It was confirmed that a change in the relative phase can be measured by monitoring the shift in the interference fringe and that Raman emissions generated by four-wave Raman mixing are phase locked.

DOI： 10.1007/s00340-017-6732-9

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.optlastec.2016.09.010

Language：English   Publishing type：Research paper (scientific journal)  

Structural isomers and enantiomers of hexachlorocyclohexane (HCH) were separated using a chiral column by gas chromatography and quantitatively determined by multiphoton ionization mass spectrometry using an ultraviolet femtosecond laser (200 and 267 nm) as the ionization source. The order of elution of the enantiomers (i.e., (+)-alpha-HCH and (-)-alpha-HCH) was predicted from stabilization energies calculated for the complexes using permethylated gamma-cyclodextrin as the stationary phase of the column, and the results were compared with the experimental data. The molecular ions observed for HCH were weak, even though they can be ionized through a process of resonance enhanced two-photon ionization at 200 nm. This unfavorable result can be attributed to the dissociation of the molecular ion, as predicted from quantum chemical calculations.

DOI： 10.1007/s13361-016-1497-7

Language：English   Publishing type：Research paper (scientific journal)  

A diagnostic systemusing three frequency-resolved optical gating (FROG) techniques-crosscorrelation, second harmonic generation, and self-diffraction-is reported for the reliable characterization of femtosecond laser pulses. The latter two FROG techniques are employed to evaluate suitability in measurements of the reference pulse. A train of optical pulses generated by the superposition of two femtosecond pulses emitting at 800 nmand 1180 nmhas been characterized by the cross-correlation FROG to evaluate the reliability of the present diagnostic system.

DOI： 10.3390/app6110315

Language：English   Publishing type：Research paper (scientific journal)  

The allergenic compounds listed in the Cosmetics Directive by the Scientific Committee for Consumer Safety were analyzed by gas chromatography combined with multiphoton ionization mass spectrometry using a femtosecond laser emitting at 200 and 267 nm as the ionization source. The limits of detection were less than 100 pg/mu L for all of the compounds, permitting them to be measured in actual samples that were simply prepared by a 100-fold dilution of the original sample. The ionization process was investigated for the 26 allergens, some of which had no absorption band, even in the far-UV region. As a result, nonresonant two-photon ionization was found to be the most sensitive and universal method for the trace analysis of these compounds, because of the short pulse width, i.e., a high peak power, of the femtosecond laser used. It should be noted that the excess energy can be reduced by using a laser emitting at longer wavelengths (267 nm) and that fragmentation can be suppressed, especially for a molecule that contains a long side chain. Three commercially available perfumes were measured, and more than 10 allergenic compounds were determined.

DOI： 10.1021/acs.analchem.6b03229

Language：English   Publishing type：Research paper (scientific journal)  

To decrease health-risks to humans, non-toxic compounds were evaluated for use as internal standards for calibrating data obtained by gas chromatography/multiphoton ionization mass spectrometry (GC-MPI-MS) using an ultraviolet femtosecond laser as the ionization source. The retention time in the mass chromatogram was calibrated using a retention index, in which a series of n-alkanes was employed as internal standards for evaluating the retention times for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). To compensate for changes in signal intensity in MPI-MS, the dependence of signal intensity on the laser pulse energy was investigated for the dioxin-like compounds, in addition to five non-toxic aromatic hydrocarbons, that were used as internal standards. Based on their similar behavior,the non-toxic PCDD/PCDF, its C-13-isotope, and pentachlorobenzene behave similarly, we conclude that they can be used for calibrating the signal intensities in MPI-MS. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2016.09.071

Language：English   Publishing type：Research paper (scientific journal)  

Multicolor deep-ultraviolet femtosecond pulses are generated in a spectral range of 220-300 nm with pulse energies exceeding 1 mu J. Pulses with shorter wavelengths are also generated with the shortest wavelength of 185 nm. These pulses are generated through cascaded four-wave mixing induced in hydrogen gas by use of three-color femtosecond pump pulses at 1200, 800, and 267 nm. The third pulse dramatically enhances the intensities of the multicolor deep-ultraviolet pulses. The cross-phase modulation induced by the two intense near-infrared pulses broadens the spectral width of each multicolor emission, resulting in a spectral width supporting a transform-limited duration shorter than 10 fs.

DOI： 10.1007/s00340-016-6493-x

Language：English   Publishing type：Research paper (scientific journal)  

Multiphoton ionization processes of parent-polycyclic aromatic hydrocarbons (PPAHs), nitro-PAHs (NPAHs), and amino-PAHs (APAH5) were examined by gas chromatography combined with time-of-flight mass spectrometry using a femtosecond Ti:sapphire laser as the ionization source. The efficiency of multiphoton ionization was examined using lasers emitting in the far-ultraviolet (200 nm), deep ultraviolet (267 nm), and near-ultraviolet (345 nm) regions. The largest signal intensities were obtained when the far-ultraviolet laser was employed. This favorable result can be attributed to the fact that these compounds have the largest molar absorptivities in the far-ultraviolet region. On the other hand, APAH5 were ionized more efficiently than NPAHs in the near-ultraviolet region because of their low ionization energies. A sample extracted from a real particulate matter 2.5 (PM2.5) sample was measured, and numerous signal peaks arising from PAH and its analogs were observed at 200 nm. On the other hand, only a limited number of signed peaks were observed at 345 nm, some of which were signed to PPAHs, NPAHs, and APAHs. Thus, multiphoton ionization mass spectrometry has potential for the use in comprehensive analysis of toxic environmental pollutants. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.chemosphere.2016.02.114

Language：English   Publishing type：Research paper (scientific journal)  

The efficiencies of resonant and nonresonant multiphoton ionization in the femtosecond region
Ionization efficiency in mass spectrometry was examined for three types of molecules under different ionization schemes, i.e., resonant/nonresonant and two-photon/three-photon ionization, using an ultraviolet (UV) femtosecond laser at different wavelengths, pulse energies, and pulse widths. The efficiency of nonresonant ionization could be improved substantially by decreasing the laser pulse width. The effect of resonance was minimal when an ultrashort optical pulse of less than 100 fs was employed for ionization in the UV region. Three-photon ionization was less efficient than two-photon ionization, but the difference was not significant at shorter pulse widths in the femtosecond region. Although the excess energy can be decreased by optimizing the laser wavelength in the case of nonresonant ionization, fragmentation was not suppressed in the cases studied here. However, fragmentation was drastically suppressed when the laser pulse width was decreased. Thus, this approach of using an ultrashort optical pulse would provide a new tool for soft ionization and then for more reliable identification of an analyte.

DOI： 10.1039/c6an00577b

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

A simple method was proposed for on-site evaluation of the pulse width of an ultraviolet femtosecond laser coupled with a mass spectrometer. This technique was based on measurement of a two-photon ionization signal in mass spectrometry by translation of the prism in the pulse compressor of the femtosecond laser. The method was applied to optical pulses that were emitted at wavelengths of 267, 241, and 219 nm; the latter two pulses were generated by four-wave Raman mixing using the third harmonic emission of a Ti:sapphire laser (267 nm) in hydrogen gas. The measurement results show that this approach is useful for evaluation of the pulse width of the ultraviolet femtosecond laser used in mass spectrometry for trace analysis of organic compounds.

DOI： 10.3390/app6050136

Language：English   Publishing type：Research paper (scientific journal)  

Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200 nm) of a femtosecond Ti:sapphire laser (800 nm) were employed. The signal intensities were found to be greater when measured at 200 nm compared with those measured at 267 nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.talanta.2015.11.054

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Particulate matter 2.5 (PM2.5), collected from ambient air in Fukuoka City, was analyzed by gas chromatography combined with multiphoton ionization mass spectrometry using an ultraviolet femtosecond laser (267 nm) as the ionization source. Numerous parent polycyclic aromatic hydrocarbons (PPAHs) were observed in a sample extracted from PM2.5, and their concentrations were determined to be in the range from 30 to 190 pg/m(3) for heavy PPAHs. Standard samples of nitrated polycyclic aromatic hydrocarbons (NPAHs) were examined, and the limits of detection were determined to be in the picogram range. The concentration of NPAH adsorbed on PM2.5 in the air was less than 900-1300 pg/m(3).

DOI： 10.1007/s13361-015-1276-x

Language：English   Publishing type：Research paper (scientific journal)  

In optical modulation, the highest available modulation rate is basically limited to the GHz frequency range at best. This is because optical modulation is often performed using electro-optic or acousto-optic effects that require application of an external signal to solid-state nonlinear optical materials. Here we describe optical modulation of continuous-wave radiation at frequencies exceeding 10 THz based on ultrafast variation of molecule polarizability arising from coherent molecular motion. The optical modulation efficiency is extensively enhanced by fulfilling phase-matching conditions with the help of dispersion control of the optical cavity, generating sidebands with a highest ratio of 7.3 x 10(-3). These results will pave the way for development of versatile optical modulation-based techniques in a wide range of research fields in optical sciences, such as mode-locked lasers operating in the THz range.

DOI： 10.1038/srep20908

Language：English   Publishing type：Research paper (scientific journal)  

Three color continuous-wave (CW) laser emissions with constant frequency separation are generated in the near-infrared (NIR) region using a dispersion-compensated optical cavity filled with hydrogen gas. By focusing these laser emissions into second-harmonic generation (SHG) crystals, multiple second harmonic signals and sum-frequency signals are generated in the near-ultraviolet (NUV) with a constant frequency spacing. Up to five colors of these NUV CW laser emissions can be generated simultaneously by using SHG crystals with different orientations. The interference between the second-harmonic signal of one NIR laser emission and the sum-frequency signal of the other two NIR emissions was observed experimentally, indicating mutual phase coherence among the NIR laser emissions. The phase coherence allows the synthesis of a train of ultrashort pulses with a THz repetition rate in both the NUV and the NIR by using the CW emission lines. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2015.10.019

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Four-wave optical parametric amplification (FWOPA) in a Raman-active medium is experimentally investigated by use of an air-filled hollow fiber. A femtosecond pump pulse shorter than the period of molecular motion excites the coherent molecular motion of the Raman-active molecules during the parametric amplification of a signal pulse. The excited coherent motion modulates the frequency of the signal pulse during the parametric amplification, and shifts it to lower frequencies. The magnitude of the frequency redshift depends on the pump intensity, resulting in intensity-dependent spectral characteristics that are different from those in the FWOPA induced in a noble-gas-filled hollow fiber.

DOI： 10.3390/photonics2030933

Language：English  

DOI： 10.1016/j.talanta.2015.03.027

Language：English   Publishing type：Research paper (scientific journal)  

In order to suppress the fragmentation and improve the sensitivity for determination of nitrated polycyclic aromatic hydrocarbons (NPAHs), the mechanism of multiphoton ionization was studied for the following representative NPAHs, 9-nitroanthracene, 3-nitrofluoranthene, and 1-nitropyrene. The analytes were extracted from the PM2.5 on the sampling filter ultrasonically, and were measured using gas chromatography/multiphoton ionization/time-of-flight mass spectrometry with a femtosecond tunable laser in the range from 267 to 405 nm. As a result, a molecular ion was observed as the major ion and fragmentation was suppressed at wavelengths longer than 345 nm. Furthermore, the detection limit measured at 345 nm was measured to be the subpicogram level. The organic compounds were extracted from a 2.19 mg sample of particulate matter 2.5 (PM2.5), and the extract was subjected to multiphoton ionization mass spectrometry after gas chromatograph separation. The background signals were drastically suppressed at 345 nm, and the target NPAHs, including 9-nitroanthracene and 1-nitropyrene, were detected, and their concentrations were determined to be 5 and 3 pg/m(3), respectively. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.talanta.2015.03.027

Language：English   Publishing type：Research paper (scientific journal)  

Fluorescence lifetime imaging microscopy was applied to evaluate the efficacy of anticancer drugs. A decrease in the fluorescence lifetime of the nucleus in apoptotic cancer cells stained by SYTO 13 dye was detected after treatment with antitumor antibiotics such as doxorubicin or epirubicin. It was confirmed that the change in fluorescence lifetime occurred earlier than morphological changes in the cells. We found that the fluorescence lifetime of the nucleus in the cells treated with epirubicin decreased more rapidly than that of the cells treated with doxorubicin. This implies that epirubicin was more efficacious than doxorubicin in the treatment of cancer cells. The change in fluorescence lifetime was, however, not indicated when the cells were treated with cyclophosphamide. The decrease in fluorescence lifetime was associated with the processes involving caspase activation and chromatin condensation. Therefore, this technique would provide useful information about apoptotic cells, particularly in the early stages.

DOI： 10.1088/2050-6120/3/2/025006

Language：English   Publishing type：Research paper (scientific journal)  

A gas was utilized in producing the third harmonic emission as a nonlinear optical medium for autocorrelation and frequency-resolved optical gating measurements to evaluate the pulse width and chirp of a Ti:sapphire laser. Due to a wide frequency domain available for a gas, this approach has potential for use in measuring the pulse width in the optical (ultraviolet/visible) region beyond one octave and thus for measuring an optical pulse width less than 1 fs.

DOI： 10.3390/app5020136

Language：English   Publishing type：Research paper (scientific journal)  

The generation of intense subcycle laser pulses during the propagation of two-color femtosecond pulses in a gas medium is investigated theoretically and experimentally. Four-wave mixing induced by the laser pulses in a gas medium generates multi-octave laser radiation from the ultraviolet to the infrared, which forms stable subcycle laser pulses after a certain propagation distance in a gas medium with group-velocity dispersion. The intense subcycle laser pulses would allow the coherent control of the waveforms of soft-x-rays generated via high-harmonic generation. (C) 2015 Optical Society of America

DOI： 10.1364/OE.23.012373

Language：English   Publishing type：Research paper (scientific journal)  

Multiphoton ionization processes were studied for three types of explosives using a line-tunable ultraviolet femtosecond laser. When peroxides such as triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) were ionized through a nonresonant two-photon process, a molecular ion was dominantly observed by reducing the excess energy remaining in the ion. However, an aromatic nitro compound such as 2,4,6-trinitrotoluene (TNT) produced large signals arising from molecular and fragment ions by resonant two-photon ionization. In addition, only fragment ions were produced from a nonaromatic nitro compound such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), even when a resonant two-photon ionization process was employed, suggesting that a further reduction in excess energy would be necessary if a molecular ion were to be observed.

DOI： 10.1021/ac504667t

Language：English   Publishing type：Research paper (scientific journal)  

Triacetone triperoxide (TATP), an explosive compound, was measured using gas chromatography combined with multiphoton ionization time-of-flight mass spectrometry (GC/MPI-TOFMS). By decreasing the pulse width of a femtosecond laser from 80 to 35 fs, a molecular ion was drastically enhanced and was measured as one of the major ions in the mass spectrum. The detection limits obtained using the molecular (M center dot+) and fragment (C2H3O+) ions were similar or slightly superior to those obtained using conventional mass spectrometry based on electron and chemical ionization. In order to improve the reliability, an isotope of TATP, i.e., TATP-d18, was synthesized and used as an internal standard in the trace analysis of TATP in a sample of human blood. TATP could be identified in a two-dimensional display, even though numerous interfering compounds were present in the sample. Acetone, which is frequently used as a solvent in sampling TATP, produced a chemical species with a retention time nearly identical to that of TATP and provided a C2H3O+ fragment ion that was employed for measuring a chromatogram of TATP in conventional MS. This compound, the structure of which was assigned as phorone, was clearly differentiated from TATP based on a molecular ion observable in MPI-TOFMS. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2014.10.045

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrate phase-matched nondegenerate four-wave mixing (FWM) in a high-finesse optical cavity using a gaseous Raman-active medium pumped by two independent continuous-wave lasers. Efficient upconversion is achieved for pump beams at different wavelengths under phase-matched conditions by optimizing the total dispersion of the hydrogen-filled optical cavity. The independent control of the pump-beam polarizations leads to further enhancement of the upconversion efficiency arising from a larger Raman gain than that in degenerate FWM. This approach offers a promising alternative for a narrow-linewidth tunable light source for highly precise laser spectroscopy. (C) 2014 Optical Society of America

DOI： 10.1364/OL.40.000073

Language：English   Publishing type：Research paper (scientific journal)  

Excitation energies, oscillator strengths, and vacuum-ultraviolet/deep-ultraviolet absorption spectra were calculated for nerve agents, such as sarin, soman, VX, tabun, mustard gas, and analogs. We used time-dependent density functional theory (TD-DFT) methods that included B3LYP combined with basis sets of cc-pVDZ and cc-pVTZ, and omega B97XD with cc-pVTZ. The vertical ionization energies were also calculated for these compounds, in order to collect additional information relative to the optimal pathways for multiphoton ionization in mass spectrometry.

DOI： 10.2116/analsci.30.1113

Language：English   Publishing type：Research paper (scientific journal)  

Four-wave Raman mixing (FWRM) in molecular hydrogen was studied using chirped pump and Stokes pulses emitting at 802 and 1,203 nm, respectively. The group delay dispersion (GDD) of the anti-Stokes pulse was examined employing a frequency-resolved optical gating system at different GDDs of the pump and Stokes pulses (0 or +/- 1,000 fs(2)). As a result, the energy and the sign of GDD for the anti-Stokes pulse remained unchanged, when the pump and Stokes pulses had the GDD with the same sign. When the sign was not the same, the energy decreased and only the portion useful for resonant FWRM was converted into a Raman emission. This technique has a potential for use in compensation of dispersion by passing the negatively chirped high-order Raman sidebands through the optics with positive chirps in the spectral region from the deep-ultraviolet to the near-infrared, to generate multiple transform-limited Raman pulses and then to produce an ultrashort optical pulse by a Fourier synthesis of these Raman emissions.

DOI： 10.1007/s00340-014-5887-x

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrate the generation of continuous-wave Stokes and anti-Stokes Raman sidebands including the three-primary-color (683, 532, and 436 nm) components. The Raman sidebands are generated through both stimulated and coherent anti-Stokes Raman scattering in a broadband high-finesse optical cavity filled with gas-phase hydrogen as a Raman-active medium and covering the entire visible spectral range (420-680 nm). The blue emission is considerably enhanced by matching the frequency with one of the longitudinal modes of the optical cavity, and high conversion efficiencies are observed when the coherent length corresponds to an integral multiple of the round-trip length of the optical cavity. This indicates that phase-matching plays a critical role in determining the efficiency of the Raman comb generation.

DOI： 10.1007/s00340-014-5856-4

Language：English   Publishing type：Research paper (scientific journal)  

Amplification of supercontinuum light via four-wave optical parametric amplification in a gas-filled hollow fiber is investigated. By pumping with a femtosecond pulse in the near-infrared, amplification was observed in the wavelength range 500-700 nm, with an amplification gain up to 100. The amplification bandwidth obtained here supports sub-10-fs pulse durations. The wavelength and gas-pressure dependence of the amplification gain in this regime significantly differ from those predicted from only the linear phase mismatch. The nonlinear phase mismatch, arising from nonlinear phase modulations induced by a pump pulse, dominates the features observed for the amplification, i.e., a low phase-matching pressure and an amplification gain depending on wavelength. To investigate the effect of phase modulations on the parametric amplification, numerical analysis and simulations are used to reproduce the measured wavelength dependence of the amplification gain.

DOI： 10.1007/s00340-013-5751-4

Language：English   Publishing type：Research paper (scientific journal)  

We investigate four-wave mixing in hydrogen gas using a gas cell and a hollow fiber for the generation of high-energy, multicolor femtosecond (fs) optical pulses. Both a hydrogen-filled gas cell and hollow fiber lead to the generation of multicolor fs pulses in a broad spectral range from the deep ultraviolet to the near infrared. However, there is a difference in the energy distribution of the multicolor emission between the gas cell and the hollow fiber. The hydrogen-filled gas cell generates visible pulses with higher energies than the pulses created by the hollow fiber. We have generated visible pulses with energies of several tens of microjoules. The hydrogen-filled hollow fiber, on the other hand, generates ultraviolet pulses with energies of a few microjoules, which are higher than the energies of the ultraviolet pulses generated in the gas cell. In both schemes, the spectral width of each emission line supports a transform-limited pulse duration shorter than 15 fs. Four-wave mixing in hydrogen gas therefore can be used for the development of a light source that emits sub-20 fs multicolor pulses in a wavelength region from the deep ultraviolet to the near infrared with microjoule pulse energies.

DOI： 10.3390/app4030318

Language：English   Publishing type：Research paper (scientific journal)  

A frequency-resolved optical gating (FROG) technique that combines autocorrelation (second-harmonic-generation FROG, SHG-FROG) and cross correlation FROG (XFROG) is reported for simultaneous characterization of two unknown optical pulses. Two SHG-FROG signals and a XFROG signal are acquired in a single measurement using a single diagnostic system. Unlike the conventional combination of SHG-FROG for reference-pulse characterization and XFROG for test-pulse characterization, the ambiguity in the direction of time in SHG-FROG is removed during phase retrieval by simultaneously analyzing the three FROG signals. Furthermore, overall characterization is faster, more robust, and highly convergent than the conventional combination of SHG-FROG and XFROG techniques. (C) 2014 Optical Society of America

DOI： 10.1364/OL.39.003006

Language：English   Publishing type：Research paper (scientific journal)  

To enhance sensitivity in multiphoton ionization/time-of-flight mass spectrometry, the sample, in the form of an effusive molecular flow, was introduced at a small angle relative to the laser beam. This approach enlarged the volume of interaction between the sample and the laser beam, thus increasing the number of ions formed by multiphoton ionization. The sensitivity obtained using this technique was compared with that obtained using a previous method based on the off-axis sample introduction technique with detection limits for organic hydrocarbons at the subfemtogram level. The detection limit was examined for dioxins and an improvement of 2.5 +/- 0.4 fold was found. The technique developed herein is applicable for practical ultratrace analysis of persistent organic pollutants.

DOI： 10.2116/analsci.30.445

Language：English   Publishing type：Research paper (scientific journal)  

An autocorrelator consisting of a time-of-flight mass spectrometer as a two-photon-response detector was constructed for use in measuring an optical pulse width based on non-resonant two-photon ionization. An organic compound that can be two-photon ionized in a wide spectral region has the potential for use in measuring an optical pulse width approaching 1 fs. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2013.07.055

Language：English  

We present a novel, cavity-enhanced spectroscopic technique based on a phase-matched Raman process to detect trace quantities of gas. The essence of this technique is the careful control of cavity dispersion to satisfy the phase-matching condition of coherent anti-Stokes Raman scattering (CARS) enhanced in a high-finesse optical cavity. A 6000-fold improvement of the CARS signal is observed under optimized conditions, indicating that this is a promising tool to quantify Raman-active molecules with an extremely low detection limit.

DOI： 10.2116/analsci.30.75

Language：English   Publishing type：Research paper (scientific journal)  

The temporal profile of the second and third harmonic emissions of a Ti:sapphire laser was measured using an autocorrelator consisting of a mass spectrometer as a two-photon-response detector. A number of organic compounds that are potentially applicable for two-photon excitation and subsequent one-photon ionization were investigated using density functional theory calculations. N,N'-dimethylaniline and acetonitrile were used for the measurement of the pulse width for the second and third harmonic emissions of the Ti:sapphire laser. This approach has the potential for use in measuring pulse widths as short as 1-3 fs in the ultraviolet region.

DOI： 10.1007/s00340-013-5505-3

Language：English   Publishing type：Research paper (scientific journal)  

The fourth harmonic emission (200 nm) of a femtosecond Ti:sapphire laser (35 fs) was generated and used in the multiphoton ionization of 49 pesticides in gas chromatography/time-of-flight mass spectrometry. The limit of detection was improved when the ionization source from the third harmonic emission (267 nm) was replaced with the fourth harmonic emission for several pesticide molecules that contained no conjugated double bonds since their absorption bands are located in the far-ultraviolet region. This analytical instrument was used in the analysis of a series of real samples including potatoes, carrots, and cabbage, and a signal suspected to arise from di-allate was observed for the potato sample.

DOI： 10.1007/s00216-013-6976-0

Language：English   Publishing type：Research paper (scientific journal)  

Fluorescence lifetime imaging microscopy (FLIM) was used to monitor the interaction between androgen receptor (AR) tagging of a green fluorescent protein (GFP) and the ligands in living cells. The fluorescence lifetime of the AR-GFP without ligands was ca. 3.1ns, which was reduced to ca. 2.5ns after treatment with agonist 5 alpha-dihydrotestosterone. On the other hand, the fluorescence lifetime of AR-GFP was not changed after treatment with antagonist hydroxyflutamide. The reaction kinetics was simulated in the present study, and the obtained results indicated the possibility of the presence of an intermediate complex during the reaction. FLIM can be used to record the ratio of the AR as it reacts with an agonist, and, therefore, it is useful for acquiring information concerning the interaction between AR and ligands in living cells.

DOI： 10.1248/cpb.c12-00428

Language：English   Publishing type：Research paper (scientific journal)  

A simple pretreatment procedure was developed for the analysis of dioxins in soil samples using gas chromatography/multiphoton ionization/time-of-flight mass spectrometry. The sample was subjected to a pressurized liquid extraction procedure, followed by separation using a pair of Sulfoxide and Ag-ION columns for cleanup. Due to the high selectivity of laser ionization, the procedure was simplified and the time required for an analysis was decreased to 3 h. The sample collected after the earthquake and tsunami contained relatively high concentrations of PCBs and PCDD/Fs. This simple and rapid pretreatment procedure can be useful for monitoring the environment to prevent unexpected exposure of toxic dioxins for the workers who have to process more than 20 million tons of the wastes in a few years.

DOI： 10.1021/ac3028917

Language：English   Publishing type：Research paper (scientific journal)  

A two-color pump beam consisting of a fundamental beam of a Ti: sapphire laser (35 fs, 802 nm) and a signal beam generated by optical parametric amplification (55 fs, 1203 nm) was utilized to generate multiple Raman sidebands by vibrational four-wave Raman mixing. The second harmonic emission (401 nm) was further employed as a seed beam for enhancing efficiency. Numerous sidebands emitting at 602, 481, 344, 301, 267, 241, 219, 200, and 185 nm were observed by irradiating the beam onto a screen coated with sodium salicylate. The spectral band width of these emission lines was capable of generating 0.9-fs optical pulses by Fourier synthesis. (C) 2012 Optical Society of America

DOI： 10.1364/OE.20.027959

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Here, we report the detection of native amino acids using a sheath-flow electrochemical detector with a working electrode made of copper wire. A separation capillary that was inserted into a platinum tube in the detector acted as a grounded electrode for electrophoresis and as a flow channel for sheath liquid. Sheath liquid flowed outside the capillary to support the transport of the separated analytes to the working electrode for electrochemical detection. The copper wire electrode was aligned at the outlet of the capillary in a wall-jet configuration. Amino acids injected into the capillary were separated following elution from the end of the capillary and detection by the copper electrode. Three kinds of copper electrodes with different diameters50, 125, and 300 mu mwere examined to investigate the effect of the electrode diameter on sensitivity. The peak widths of the analytes were independent of the diameter of the working electrode, while the 300-mu m electrode led to a decrease in the signal-to-noise ratio compared with the 50- and 125-mu m electrodes, which showed no significant difference. The flow rate of the sheath liquid was also varied to optimize the detection conditions. The limits of detection for amino acids ranged from 4.4 to 27 mu M under optimal conditions.

DOI： 10.1002/elps.201200059

Language：English   Publishing type：Research paper (scientific journal)  

A time-of-flight mass spectrometer was constructed for use in detecting negatively charged species induced by laser multiphoton ionization. Mass spectra, collected for a variety of compounds, contained several signal peaks. Their flight times were, however, an order of magnitude shorter than the values predicted based on the length of the flight region. To clarify this curious phenomenon, a simple molecule, namely, nitric oxide was measured for calibration of the flight times and for assignment of the signal peaks. A careful investigation led to a possible mechanism, in which the signals do not arise from negative ions but arise from electrons generated at the surface of the repeller electrode by collisions of positive ions that are formed by multiphoton ionization of the analyte in a molecular beam.

DOI： 10.2116/analsci.28.683

Language：English   Publishing type：Research paper (scientific journal)  

The frequency domain of non-resonant two-photon ionization, defined as a frequency separation from half of the ionization energy to the excitation energy, was investigated using density functional theory calculations. Several organic compounds have the potential for use in the measurement of the ultrashort optical pulse width in the ultraviolet region using an autocorrelator consisting of a mass spectrometer as a two-photon-response detector. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2012.04.015

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A low-energy, high-repetition-rate picosecond laser (40 mu J, 20 kHz, 258 nm) was used for multiphoton ionization (MPI) in gas chromatography/time-of-flight mass spectrometry to quantitatively determine dioxins (DXNs) and polycyclic aromatic hydrocarbons (PAHs). The sensitivity of the technique was compared with that obtained using a high-energy, low-repetition-rate femtosecond laser (86 mu J, 1 kHz, 261 nm). The limits of detection (LODs) for the picosecond laser were several femtograms for chlorinated DXNs with low numbers of chloro substituents, and were several times lower than values obtained using a femtosecond laser, although the LODs were increased, reaching values that were nearly identical to those for the femtosecond laser for octachlorodibenzo-p-dioxin (octaCDD) and octachlorodibenzofuran (octaCDF). The LODs were also measured for 16 PAHs specified by the United States Environmental Protection Agency; the values for half of these compounds were at sub-femtogram levels. The procedure was used to analyze a surface-water sample collected from a river.

DOI： 10.2116/analsci.28.445

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrate the generation of continuous-wave (cw) Raman sidebands through phase-matched four-wave mixing (FWM) in molecular hydrogen. The phase-matching conditions of the intracavity FWM driven in our dispersion-compensated high-finesse cavity are satisfied over a 52.8 THz-wide frequency range (763.9-883.6 nm). This leads to the generation of high-order anti-Stokes emission. The cw Raman sidebands have sufficient bandwidth to allow the synthesis of a train of optical pulses with a duration of 13 fs at a repetition rate of 17.6 THz under phase-locked conditions. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2011.09.054

Language：English   Publishing type：Research paper (scientific journal)  

An authentic mixture of polychlorinated biphenyls was measured using a short wide-bore capillary column for the group separation of major components present in an actual sample of Kanechlor. The limits of detection were improved by ca. 2 fold in comparison with those obtained using a conventional capillary column, since the retention time was reduced and the amount of analytes introduced into the mass spectrometer per unit time could be increased. On the other hand, surface-water and sediment samples containing polycyclic aromatic hydrocarbons (PAHs) were collected from the river located in the vicinity of a waste water treatment plant. Even acenaphthylene, a minor component of the mixture could be measured for the sediment sample, and the concentrations were determined for several heavy PAHs. As demonstrated, a technique involving laser multiphoton ionization/time-of-flight mass spectrometry was useful as a sensitive and selective analytical tool for the trace analysis of persistent organic pollutants in an environmental sample. © 2011 Higher Education Press and Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/s11783-011-0374-7

Language：English   Publishing type：Research paper (scientific journal)  

Polyacrylamide gel electrophoresis (PAGE) is used frequently for isolation and purification of DNA fragments. In the present study, DNA fragments extracted from polyacrylamide gels showed significant band broadening in capillary electrophoresis (CE). A pHY300PLK (a shuttle vector functioning in Escherichia coli and Bacillus subtilis) marker, which contained nine fragments ranging from 80 to 4870?bp, was separated by PAGE, and each fragment was isolated by phenol/chloroform extraction and ethanol precipitation. After extraction from the polyacrylamide gel, the peaks of the isolated DNA fragments exhibited band broadening in CE, where a linear poly(ethylene oxide) was used as a sieving matrix. The theoretical plate numbers of the DNA fragments contained in the pHY300PLK marker were >106 for all the fragments before extraction. However, the DNA fragments extracted from the polyacrylamide gel showed decreased theoretical plate numbers (520 times smaller). The degradation of the theoretical plate number was significant for middle sizes of the DNA fragments ranging from 489 to 1360?bp, whereas the largest and smallest fragments (80 and 4870?bp) had no obvious influence. The band broadening was attributed to contamination of the DNA fragments by polyacrylamide fibers during the separation and extraction process.

DOI： 10.1002/jssc.201100909

Language：English   Publishing type：Research paper (scientific journal)  

This paper describes a sample inlet system with several advantages over other pulsed valves, as applied to resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry. The nozzle is based on online concentration by analyte adsorption/laser desorption (online COLD), where a capillary column with a narrowly synthesized tip is employed for sample introduction. The analyte molecules adsorbed at the tip are desorbed by a pulsed laser and are injected into a mass spectrometer as a packet. The online COLD nozzle can produce very short gas pulses on the order of 1 mu s. Moreover, this nozzle is capable of operating over a wide range of repetition rates from 1 Hz to 1 kHz. In addition, this nozzle intrinsically possesses several unique characteristics; for instance, it can be heated to very high temperatures and has nearly zero dead volume. Therefore, the present sample introduction technique offers an ideal and versatile nozzle for laser ionization/mass spectrometry. (C) 2012 American Institute of Physics. [doi:10.1063/1.3675890]

DOI： 10.1063/1.3675890

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

The generation of a multifrequency continuous-wave laser through stimulated Raman scattering and phase-matched four-wave mixing in a medium-filled optical cavity is demonstrated. Three different quantum pathways for the four-wave mixing, two of them degenerate and one of them nondegenerate, can be excited independently by tuning the intracavity dispersion. The results suggest that phase-matched Raman sidebands were generated on the longer wavelength side as well as on the shorter wavelength side, which can be used for the Fourier synthesis of a train of ultrashort optical pulses. (C) 2011 Optical Society of America

DOI： 10.1364/OE.19.024298

Language：English   Publishing type：Research paper (scientific journal)  

Cell membrane transporter-proteins have been partly implicated in lowering the accumulation of drugs in cancer cells, leading to multidrug resistance (MDR). Two cancer cell lines, A549 and RDES, were continuously exposed to subclinical concentration (250 nM) of anthracyclines and micellar electrokinetic chromatography was used to investigate their in vitro accumulation after treatment with inhibitors of membrane transporter-proteins. The four anthracylines [doxorubicin (DOX), epirubicin (EPI), daunorubicin (DNR), and idarubicin (IDA)] were separated within a short analysis time of less than 15 min in borate buffer (80 mM, pH 9.22) containing sodium taurodeoxycholate (35 mM), 2-hydroxypropyl-.-cyclodextrin (3.5% wt/v), and sodium dodecylsulfate (20 mM). Laser-induced fluorescence was used for detection of the anthracyclines. Three inhibitors, verapamil, cyclosporine A and probenecid, were examined by adding each inhibitor independently or two inhibitors simultaneously to the culture medium. It was found that independent use of each inhibitor leads to more efficient accumulation than combined use of verapamil and probenecid. In addition, the results show that effect of inhibitors on the accumulation of anthracyclines depended on type of cell: in RDES, inhibitors enhanced accumulation of all four anthracyclines, while in A549, inhibitors showed different accumulation behavior for each anthracycline. Generally higher accumulation of anthracyclines was observed in RDES cells than A549, as evidenced by dead cells (7-16%) after 24 h of continuous exposure to subclinical concentration. Copyright (C) 2011 John Wiley & Sons, Ltd.

DOI： 10.1002/bmc.1589

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography combined with multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) using ultraviolet picosecond and femtosecond lasers was employed to quantitatively analyze a series of polybrominated diphenyl ethers (PBDEs). Congeners from monoBDE to tetraBDEs were analyzed using a picosecond laser emitting at 266 nm. In order to enhance the efficiency of ionization for highly brominated DEs via triplet levels, a different laser emitting at 213 nm was used. It was, however, difficult to quantify such congeners, even at this wavelength. This unexpected result can be explained by the photodecomposition of PBDEs from the triplet levels. On the other hand, all congeners from monoBDE to decaBDE were detected when a femtosecond laser emitting at 267 nm was employed. Interestingly, the isomers having a smaller number of Br atoms at the meta-positions were more efficiently ionized, and provided lower values of detection limit.

DOI： 10.1039/c1ay05355h

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOFMS) was utilized for analysis of a standard mixture sample containing 49 pesticides and 4 real samples using the third-harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (100 fs) as the ionization source. A sample of a standard mixture of n-alkane was also measured for calibration of the retention time indices of the pesticides. Two photons are required for the excitation of n-alkane due to an absorption band located in the far ultraviolet region (140 nm). The n-alkane molecule in the excited state was subsequently ionized either directly or by absorbing another photon because of a high ionization potential. Due to a large excess of energy, the molecular ion was decomposed and formed many fragment ions. Compared to n-alkanes, most of the pesticides were softly ionized by the femtosecond laser: one photon was used for excitation and another was used for the subsequent ionization. The pesticides with no conjugated double bond had a lower ionization efficiency. The present analytical instrument was applied to several samples prepared from a variety of vegetables and a single fruit after pretreatment with solid-phase extraction. Three pesticides were found in these samples, although some of them were not detected by conventional GC/EI/MS-MS due to insufficient sensitivity and selectivity. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2011.06.003

Repository Public URL： http://hdl.handle.net/2324/25616

Language：English   Publishing type：Research paper (scientific journal)  

The frequency of a continuous-wave laser was converted via high-order stimulated Raman scattering and four-wave Raman mixing in a high-finesse optical cavity. The threshold for the generation of a Stokes beam was determined by the Raman gain coefficient and the loss in the cavity. The intracavity power of the second-order Stokes beam increased with an increase in pump power, whereas the power of the first-order Stokes beam stayed constant. The output power of the anti-Stokes beam was low when there was a phase mismatch between the pump and the first-order Stokes beam. The anti-Stokes beam, however, was enhanced by decreasing the pressure of the Raman active medium. This suggests that the dispersion can be used to improve the efficiency of the intracavity four-wave Raman mixing.

DOI： 10.1109/JQE.2011.2159362

Language：English   Publishing type：Research paper (scientific journal)  

The interferometric measurement of an ultrashort optical pulse is demonstrated using three-photon ionization of Xe in a time-of-flight mass spectrometer (MS). This approach allowed measurement of the third-order fringe-resolved autocorrelation trace of an ultrashort optical pulse in the deep-ultraviolet (DUV) region. The pulse can be measured in situ using the same MS that is employed in ultrafast spectroscopy. Sensitivity (> 3x10(7) W) was sufficient to measure a DUV pulse used in such applications. This setup has the potential to measure the temporal duration of a broadband (204-306 nm) ultrashort optical pulse with no additional distortion in the temporal characteristics.

DOI： 10.1007/s00340-010-4324-z

Repository Public URL： http://hdl.handle.net/2324/25514

Language：English   Publishing type：Research paper (scientific journal)  

The adenosine triphosphate (ATP) binding-cassette (ABC) transporters are a superfamily of cellular proteins that have been partly implicated as a cause of multidrug resistance (MDR) in cancer cells. The ABC superfamily consists of P-glycoprotein, multidrug resistance-associated proteins (MRP) and breast cancer-related proteins, of which MRP is of particular interest because of its ability to efflux a broader range of substrates. Since MRP1 is the most prominent member of the MRP family, a simple technique is needed for its quantification. We developed a simple, fast (total analysis time of 3 h) capillary electrophoresis immunoassay (CEIA) for the quantification of MRP1 in cancer cells. MRP1 antibody was labeled with fluorescein isothiocyanate. The labeled antibody was incubated with the cell lysate for a fixed interval (1 h), after which the cell lysate mixture was directly injected into the capillary to separate the complex of MRP1 and its antibody from free antibody. The noncompetitive CEIA method had a limit of detection of 0.2 nM and a good linear range (1.7-14.9 x 10(4) cells), and was fairly reproducible (RSD < 10&#37;). The results showed that two cell lines. A549 and RDES, expressed MRP1 in the absence of doxorubicin (DOX), with A549 registering a higher expression. Compared to DOX-free cancer cells, there was an acceleration of MRP1 expression during the 12 h-exposure to DOX, after which the level of expression remained nearly constant as the intracellular accumulation of DOX decreased. The results obtained in this work indicate that the developed CEIA method is useful for relative quantification of MRPs in cancer cells. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2011.04.046

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) was applied to a soil sample to survey several groups of polychlorinated aromatic hydrocarbons (polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), polychlorinated diphenylethers (PCDEs), and polychlorinated terphenyls (PCTs)). The signal peaks in the two-dimensional display of GC/MS could be easily and accurately assigned from the intensity distribution of the isotope peaks, even in the presence of numerous interfering species. Using this technology, mutual interferences between organochlorine compounds can be readily recognized from the data of the two-dimensional display after a measurement, although the separation of these compounds is sometimes difficult using high-resolution magnetic-sector-type mass spectrometry. This approach, based on MPI, results in less fragmentation, and is useful for the identification of analytes. Thus, GC/MPI/TOF-MS allows for the simultaneous determination of PCDD/Fs and related compounds in real samples containing numerous interfering species.

DOI： 10.2116/analsci.27.617

Language：English   Publishing type：Research paper (scientific journal)  

A sample mixture of polychlorinated biphenyls (PCBs) was measured by gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOE-MS) using four types of laser sources. When a fourth harmonic emission (266 nm) of a picosecond Nd:YAG laser (1064 nm) was utilized, highly chlorinated PCBs larger than hepta-CBs were not observed. A fifth harmonic emission (213 nm) of the picosecond Nd:YAG laser allowed the measurement of PCBs from di-CBs to octa-CBs, and the limit of detection CLOD) was several pg for each component of PCBs. The LOD for the total amount of PCBs, which was calculated using the protocol provided by the Ministry of the Environment, Japan, was 1000 pg. The signal intensity of the congeners with chlorine atoms at the ortho positions (non-coplanar PCBs) was enhanced by using the fifth harmonic emission. When the fourth harmonic emission remaining after fifth harmonic generation was simultaneously used, the LOD for total PCBs was improved to 667 pg. The PCB sample was also measured using a third harmonic emission (267 nm) of a femtosecond Ti:sapphire laser (800 nm), providing an LOD of 677 pg. Thus, the two-color beam (266/213 nm) of a picosecond Nd:YAG laser had a comparable, or even slightly superior, performance to the more expensive femtosecond Ti:sapphire laser. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2011.03.041

Language：English   Publishing type：Research paper (scientific journal)  

Previously, we have demonstrated postcolumn derivatization of proteins separated by capillary sieving electrophoresis (CSE), in which naphthalene-2,3-dicarbaldehyde was employed as a fluorogenic labeling reagent. Standard proteins separated by CSE were reacted with naphthalene-2,3-dicarbaldehyde in the presence of 2-mercaptoethanol (2-ME) which plays a role of a reducing agent in the derivatization reaction. To improve the sensitivity, we attempted the use of ethanethiol instead of 2-ME. Ethanethiol showed 1.4- to 4.5-fold lower limits of detection for proteins than 2-ME. Furthermore, we found that 8-aminopyrene-1,3,6-trisulfonate (APTS) is a good marker for relative electrophoretic mobilities of proteins in CSE. Since APTS is a fluorescent and trivalent anion, it generates strong fluorescence and migrates faster than any of the proteins. Therefore, we employed APTS as a marker to obtain the relative electrophoretic mobilities of proteins. The present method was applied to the analyses of proteins in biological samples. Human Ewing's family tumor cell line 'RDES' was used as a sample. The cultured cells were lysed with a buffer containing Tris-HCl, NaCl, sodium dodecyl sulfate, and 2-ME. After denaturation, the lysate was directly introduced into the capillary. Several peaks, which would correspond to proteins with molecular mass ranging from 10 to 93 kDa, were found in the cell lysate. In addition, we measured a milk sample by the CSE with postcolumn derivatization. The electropherogram showed five major peaks which corresponded to alpha-lactalbumin, beta-lactoglobulin, kappa-casein, bovine serum albumin, and mixture of alpha- and beta-casein.

DOI： 10.1002/elps.201000488

Language：English   Publishing type：Research paper (scientific journal)  

Dioxins in a soil sample were measured using gas chromatography/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry coupled with different types of laser sources. The fourth-harmonic emission (266 nm) of a nanosecond Nd:YAG laser (1 ns) provided low ionization efficiency, especially for highly chlorinated dioxins/dibenzofurans (CDDs/CDFs). The ionization efficiency was improved using the fourth-harmonic emission (266 nm) of a picosecond Nd:YAG laser (4 ps), due to shorter singlet excited-state lifetimes. It was, however, difficult to efficiently ionize hepta-CDD and octa-CDD/CDF, because of their shorter lifetimes, which were induced by stronger spin-orbit coupling that led to efficient relaxation of the excited molecule to triplet levels. The ionization efficiency was substantially improved using the fifth-harmonic emission (213 nm) of the picosecond Nd:YAG laser (4 ps), in which the analyte molecule that was relaxed to triplet levels was efficiently ionized using a photon with sufficient energy for ionization, although the pulse energy obtained at 213 nm was only one-third of the pulse energy obtained at 266 nm. The limits of detection achieved for 17 toxic polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs) were 0.41-45 pg. The analytical instrument developed in the present study performed sufficiently well for the practical trace analysis of dioxins in soil samples.

DOI： 10.1021/ac101849w

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/supersonic jet/resonance-enhanced multiphoton Ionization/time-of-flight mass spectrometry (GC/SSJ/REMPI/TOF-MS) was employed for isomer-selective determination of 2 4-xylenol in river and seawater samples The sample containing 2 4-xylenol was measured using argon rather than helium as the GC carrier gas to cool the analyte molecule sufficiently The Instrumental detection limit (IDL) achieved at a flow rate of 1 mL min(-1) was 14 pg Although this value was comparable to the value (ca 10 pg) obtained by gas chromatography/electron impact/quadrupole mass spectrometry (GC/EI/QMS) When the flow rate was Increased to 8 mL min(-1) interference from the 2 5-xylenol isomer was completely suppressed The IDL was degraded to 83 or 160 pg at a flow rate of 5 or 8 mL min(-1) respectively The recovery of 2 4-xylenol from the river and the seawater samples was 85 and 93&#37; respectively The time for analysis was only 10 min per one sample in GC/SSJ/REMPI/TOF-MS These results suggest that GC/SSJ/REMPI/TOF-MS is useful for the selective measurement of 2 4-xylenol which has been designated a Class I chemical substance in the Pollutant Release and Transfer Register (PRTR) (C) 2010 Elsevier B V All rights reserved

DOI： 10.1016/j.aca.2010.09.043

Language：English   Publishing type：Research paper (scientific journal)  

A tunable single short pulse laser system with a transform-limited bandwidth pumped by a picosecond Nd:YAG laser (ca. 120 ps pulse width) is demonstrated. With this configuration, the relaxation oscillations coming from a distributed feedback dye laser cavity are completely removed. Because the pumping pulsewidth is shorter than the lifetime of dye molecule on the upper laser state, the gain of the laser medium is depleted by the first pulse. The laser wavelength could be precisely tuned with the transform-limited bandwidth (for example, a linewidth of 0.02 nm). After amplification, we obtain a single short laser pulse energy up to 500 mu J at the pulsewidth of 8.2 ps.

DOI： 10.1007/s00340-010-4211-7

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrated the efficient excitation of coherent molecular motion for the generation of high-order rotational Stokes and anti-Stokes Raman emissions using a femtosecond laser. Molecular phase modulation of a probe beam was efficiently induced by an optical beat of the pump beam emitting at two different frequencies, the separation of which corresponded to the multiplicative inverse of the period of molecular rotation. The spectral width of the probe pulse was expanded to 10 nm in the deep-ultraviolet region, suggesting the generation of a 10 fs pulse by Fourier synthesis of the emission lines. (c) 2010 American Institute of Physics. [doi:10.1063/1.3467525]

DOI： 10.1063/1.3467525

Language：English   Publishing type：Research paper (scientific journal)  

A Hadamard transform-gas chromatography/mass spectrometry (HT-GC/MS) technique was employed for the online detection of ethanol or toluene in exhaled breath after drinking or smoking, respectively. Exhaled breath samples, collected from volunteers, were directly injected into the GC inlet by a Hadamard-injector without any pretreatment. In the case of breath from a drinker, using a conventional single injection, a small ion peak (corresponding to similar to 0.1 ng of ethanol), the intensity of which was approximately equal to or less than the limit of detection. When the HT technique was applied, the signal-to-noise (S/N) ratio was dramatically improved. Furthermore, in the case of breath from a smoker, using conventional injection, a weak ion peak (corresponding to similar to 0.7 pg of toluene) was marginally detected. However, the HT technique led to an improvement in the S/N ratio, with the peak corresponding to the limit of detection. In both cases, the HT technique permitted specific components in exhaled breath to be determined, without the need for any extraction procedures. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2010.06.034

Language：English   Publishing type：Research paper (scientific journal)  

A pair of concentric capillaries was developed to mix helium, which was used as the carrier gas for gas chromatography, with argon for efficient molecular cooling by supersonic jet expansion. A simple instrument was constructed for the evaluation of nozzle diameter using the Hagen-Poiseuille equation. The effects of nozzle diameter, type of expansion gas, flow rate, and the distance from the nozzle to the observation region were investigated. Mixing argon gas with the carrier gas helium resulted in efficient molecular cooling from 30 to 10 K and the complete disappearance of the background signal from the multiphoton ionization spectrum. Consequently, the spectral selectivity was significantly improved and the nozzle was successfully applied to isomer-selective analysis of dichlorotoluenes. Since the dead volume in the nozzle was negligible, it was suitable as an interface for gas chromatography and supersonic jet/multiphoton ionization/mass spectrometry. (C) 2010 American Institute of Physics. [doi:10.1063/1.3462982]

DOI： 10.1063/1.3462982

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (GC/REMPI-TOFMS) using an ultraviolet nanosecond laser was employed in the trace analysis of polycyclic aromatic hydrocarbons (PAHs). A standard sample that contained 16 PAHs on the priority list of the Environmental Protection Agency of the United States of America (U.S. EPA) was measured. A sample of river water that had been pretreated by means of solid-phase extraction was analyzed by GC/MS based on electron impact ionization (El) and REMPI to evaluate the performance of the analytical instrument. The results suggested that REMPI is superior to El for soft ionization, and suppresses the background signal due to aliphatic hydrocarbons. Thus, GC/REMPI-TOFMS is a more reliable method for the determination of PAHs present in the environment.

DOI： 10.2116/analsci.26.841

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) was developed for trace analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The use of an ultraviolet femtosecond laser (266 nm) allowed the sensitive, as well as selective, determination of PCDD/Fs with short singlet-excited-state lifetimes; the detection limit was 19 fg for 1,3,6,8-tetraCDF. Performance of the analytical instrument was examined and was ascertained to be satisfactory for all the criteria (K0311) prescribed by the Japanese Industrial Standards (JIS). The relative ionization efficiencies of C-12-native PCDD/Fs against C-13-labeled PCDD/Fs were 1.002 +/- 0.012. This suggests that C-13-labeled isotopes can be used as internal standards with no intensity calibration and that the concentrations of PCDD/Fs can be determined to within an error of ca. 1&#37;. In addition, multiphoton ionization provides negligible levels of background interference for the real soil samples even with curtailed pretreatment. The toxicity equivalence (TEQ) of the real sample was determined using GC/MPI/TOF-MS for performance evaluation against high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). The results suggest equivalent or even superior performance for GC/MPI/TOF-MS, due to low background interference and to the ability to check the reliability of the assignment from the intensity distribution of the isotope peaks.

DOI： 10.1021/ac1009063

Language：English   Publishing type：Research paper (scientific journal)  

The spectral domain of an ultraviolet femtosecond laser was expanded by stimulated Raman scattering/four-wave Raman mixing, and the resulting laser pulse was compressed using a pair of gratings. The pulse width was then measured using an autocorrelator comprised of a Michelson interferometer equipped with a multiphoton ionization/mass spectrometer which was used as a two-photon detector. A gas chromatograph/mass spectrometer was employed to analyze triacetone triperoxide (TATP), and the molecular ion induced by multiphoton ionization was substantially enhanced by decreasing the laser pulse width.

DOI： 10.1021/ac1003773

Language：English   Publishing type：Research paper (scientific journal)  

Anthracyclines are chemotherapeutic drugs that are broadly used in the treatment of various types of solid cancers and leukemia. Herein, we report on a novel analytical method for intracellular accumulation of anthracyclines using MEKC/LIF detection. An aqueous separation system permitted the injection of cell lysates directly into the capillary. The MEKC migrating solution was made up of borate buffer at pH 9.22 containing sodium taurodeoxycholate, (2-hydroxypropyl)-gamma-CD, and SDS. The anthracyclines, Doxorubicin (DOX) and epirubicin (EPI) were detected by LIF using a Nd:YAG laser (532 nm) or an argon ion laser (488 nm) for excitation. Two cell lines, human humerus tumor cells (RDES) and human lung tumor cells (A549), were treated with a mixture of the two anthracyclines for fixed periods of time, and then intracellular concentrations were determined by injecting cell lysates directly. Recovery values of 96.0-100.8&#37; were obtained for DOX and EPI. Reproducibility quantified by RSD was less than 3.9&#37; intraday and 6.7&#37; interday at concentrations ranging between 50 and 500 nM. The uptake of EPI was found to be slightly less than that of DOX for A549, but higher levels of EPI were observed in RDES. Intracellular accumulation of anthracyclines was greater in RDES than in A549, but both types of cells excreted anthracyclines after 12 h. These results indicate that MEKC with an aqueous medium is useful for investigating intracellular uptake and accumulation of drugs, since cell lysates can be used directly with no pretreatment such as deproteination or solvent extraction of analytes.

DOI： 10.1002/elps.200900659

Language：English   Publishing type：Research paper (scientific journal)  

We proposed and demonstrated a novel method for the evaluation of optical pulse trains generated by a multifrequency continuous-wave Raman laser operating at a mode separation of 17.6 THz. This approach is based on the detection of a nonlinear signal arising from the intensity modulation of a pulse train, which should provide a useful means for measuring the deviation from phase locking of multifrequency lasers. Our results suggest that an optimization of intracavity dispersion allows the generation of phase-locked multifrequency emissions, which leads to optical pulse trains at a repetition rate in excess of 10 THz. (C) 2010 Optical Society of America

DOI： 10.1364/AO.49.001586

Language：English   Publishing type：Research paper (scientific journal)  

The technique of Hadamard transform was successfully coupled with GC/nonresonant multiphoton ionization/TOFMS, for the first time. 1,4-Dichlorobenzene and the fourth harmonic generation (266 nm) of a Nd:YAG laser were employed as a model sample and an ionization laser, respectively. A Hadamard-injector coupled with a capillary-based supersonic jet nozzle (capillary-injector) was also developed in this study. The Hadamard-injector was used to obtain the chromatogram, which was encoded by successive sample introduction based on Hadamard codes, and the capillary-injector was used for injection of GC-elutes into TOFMS. Compared with a conventional single injection method, the S/N ratios were substantially improved after inverse Hadamard transformation of the encoded chromatogram. Under optimized conditions, when Hadamard matrices of 103 and 255 were used, the S/N ratios of the signals for 1,4-dichlorobenzene (concentration level, 4 mu g/1 mL ACN) were substantially improved to 4.1- and 6.6-fold, respectively, and those improvements are in good agreement with those obtained by theory (5.1- and 8.0-fold).

DOI： 10.1002/jssc.200900662

Language：English   Publishing type：Research paper (scientific journal)  

A novel sample introduction technique, based on online concentration by analyte adsorption/laser desorption, was applied to resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPT-TOFMS). Signal enhancement and optical selectivity, based on supersonic jet spectrometry, were examined by measuring the REMPI spectra. Ibis sample introduction technique was applied at the interface of a gas chromatograph (GC) and a mass spectrometer (MS). The signal intensity was enhanced ca. 80-fold, compared with that of a conventional technique based on continuous sample introduction. The analyte molecule was selectively measured using a tunable laser emitting at a wavelength of the 0-0 transition. With the use of a desorption laser, a linear calibration curve was extended over 4 orders of magnitude. The sensitivity, selectivity, and dynamic range were all superior for this sample introduction system, as were the inherent characteristics, e.g., a near-zero dead volume and thermal durability. This system would provide a useful means for practical trace analysis of aromatic hydrocarbons by GC/REMPI-TOFMS.

DOI： 10.1021/ac902273b

Language：English  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

This paper reexamines the structures and energies of dibenzofuran and twenty PCDFs in S-1-S-3 states. It was demonstrated that, although the CIS method gives a false relative ordering of excited states, the false ordering can be remedied by the CIS(D) method. Moreover the CIS geometries of typical PCDF molecules reasonably agree with their SAC-CI geometries. It was found that molecules chlorinated at the 1- and 9-positions are twisted in the S-2 state but are planar in other states, except for 1,4,6,9-TeCDF and fully chlorinated dibenzofuran (OCDF). The twisted structure of 1,4,6,9-TeCDF occurs in the S-3 state, but the structure of OCDF is twisted in every state. We partitioned the molecule into the parent structure and four chlorine groups and measured the twist energy with reference to the ground state. Then, the S-1 <- S-0 0-0 transition energies (i = 1, 2) calculated using the CIS(D) and MP2 methods could be expressed as a multiple linear equation with components and twist energy. It was further confirmed that if the multiple linear equation is corrected for residual correlation energies of the parent structure, it can predict the S-1 <- S-0 0-0 transition energies with high precision. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.theochem.2009.08.021

Language：English   Publishing type：Research paper (scientific journal)  

The separation methods for proteins with high resolution and sensitivity are absolutely important in the field of biological sciences Capillary sieving electrophoresis (CSE) is an excellent separation technique for DNA and proteins with high resolution, while LIF permits the most sensitive detection in CSE. Therefore, proteins have to be labeled with fluorescent or fluorogenic reagent to produce fluorescent derivatives. Both precolumn and oncolumn derivatization have been employed for the labeling of proteins in CSE. However, there is no report on the postcolumn derivatization due to the limitation in the use of a standard migration buffer, despite it being a promising method for sensitive detection of proteins. Here, we show a novel postcolumn derivatization method for protein separation by CSE, using a tertiary amine as a buffer component in the running buffer. Tris, which is commonly used as a base in CSE separation buffers, was substituted by tertiary amines, 2-(diethylamino) ethanol and triethanolamine. A buffer solution containing 2-(diethylamino)ethanol or triethanolamine can be used for the CSE separation followed by the postcolumn derivatization. of proteins, since both reagents are unreactive toward a fluorogenic labeling reagent, naphthalene-2,3-dicarbaldehyde. Thus, LIF detection using the postcolumn derivatization. permits significant reduction in the LOD (by a factor of 2.4-28) of proteins, compared with conventional absorbance detection.

DOI： 10.1002/elps.200900314

Language：English   Publishing type：Research paper (scientific journal)  

Triacetone triperoxide (TATP), which is used as an explosive in acts of terrorism, was measured by means of gas chromatography/multiphoton ionization/time-of-flight mass spectrometry using a deep-ultraviolet (deep-UV) femtosecond laser as an ionization source. The fragmentation process was investigated by changing the intensity of the laser at the center axis of a molecular beam. A molecular ion was observed using a femtosecond laser, and the ratio of the intensities of the molecular and fragment ions decreased as the intensity of the laser increased. These results suggest that TATP can be efficiently ionized using a deep-UV, ultrashort optical pulse. Furthermore, fragmentation was accelerated by excess energy supplied through higher-order multiphoton processes under a strong radiation field. The detection limits obtained using the molecular ion and two dominant fragment ions, C(2)H(3)O(+) + and CH(3)(+) were determined to be 670, 83 and 150 pg, respectively. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.4225

Language：English   Publishing type：Research paper (scientific journal)  

Stimulated Raman scattering induced by a femtosecond pulse formed by two pulses, polarized orthogonally with respect to each other is reported. High-frequency and low-frequency components generated at the center of the pulse through self-phase modulation temporally overlap. The two components induce a coherent molecular rotation through stimulated Raman scattering. The amplitude of this rotation in this way is larger than that of traditional transient stimulated Raman scattering in which linearly, elliptically, and circularly polarized pulses are used.

DOI： 10.1103/PhysRevA.80.021805

Language：English   Publishing type：Research paper (scientific journal)  

An off-axis sample introduction technique was developed for improvement of mass resolution in multiphoton ionization/time-of-flight mass spectrometry. The direction of the capillary for sample introduction was inclined 30 degrees relative to the axis of ion trajectory in the time-of-flight tube for both selective and sensitive detection. This approach suppressed the excessive collisions between analyte ions and carrier gas molecules that is responsible for degradation of mass resolution.

DOI： 10.1246/cl.2009.744

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

A Supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrum (SSJ/REMPI/TOF-MS) was measured for xylenols and ethylphenols. Sharp and intense peaks were observed in the REMPI spectrum of 2,4-xylenol. and the wavelength of the peak tentatively assigned to the 0-0 transition was the longest among xylenols and ethylphenols. These results suggest that 2,4-xylenol, designated as a Class 11 chemical Substance in the Pollutant Release and Transfer Register (PRTR), can be measured sensitively and selectively even when numerous isomers are Present in the sample.

DOI： 10.2116/analsci.25.599

Language：English   Publishing type：Research paper (scientific journal)  

Hadamard transform electrophoresis combined with laser-induced fluorescence (LIF) detection on a microchip was demonstrated. A compact, diode-pumped neodymium-doped yttrium aluminum garnet laser was employed as the light source for LIF detection. The analytical conditions were optimized using rhodamine B as the analyte. Under optimal conditions, the signal-to-noise ratio (S/N) of the analyte was improved by a factor of 7.5 by means of Hadamard transformation based on a 255-order cyclic S matrix. Additionally, the relationship between fluorescence intensity and analyte concentration was linear with a correlation coefficient of 0.993 in the inverse Hadamard transformed data at the concentration range from 25 to 100 pM. The results indicate that the present method is applicable to quantitative analysis at the concentration lower than the concentration limit of detection in a conventional method. The concentration limit of detection was similar to 25 pM (the relative standard deviation of the peak height was 5.2&#37;). The present technique was successfully applied to the separation of a mixture containing 1.9 nM phenylalanine and 1.9 nM glutamic acid labeled with rhodamine B isothiocyanate. The S/Ns of the analyte peaks were improved up to similar to 10 in the inverse Hadamard transformed data derived from a 127-order cyclic S matrix, while neither peak was lower than the limit of detection (S/N < 3) in conventional microchip electrophoresis by a single injection.

DOI： 10.1063/1.3116121

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Ultrafast Molecular Optical Pulse Shaping

Language：Japanese   Publishing type：Research paper (scientific journal)  

Ultrafast Molecular Optical Pulse Shaping

Language：English   Publishing type：Research paper (scientific journal)  

A simple and selective method was developed for determination of the concentration of 2,4-xylenol in river and sea water samples using gas chromatography/mass spectrometry (GC/MS). Trace amounts of 2,4-xylenol were collected in a Oasis HLB Plus cartridge, eluted with acetonitrile. The method detection limit of 2,4-xylenol was 1.4 ng/L. The trace peaks of 2,4-xylenol were found in water samples from the river and the sea, and the concentrations were all less than 1.4 ng/L. The nine peaks of the 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5-xylenol, and o-, m-, p-ethyl phenol that gave the same m/z ratio were separated efficiently.

DOI： 10.1007/s00128-008-9594-3

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) was applied to the trace analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). To determine the optimum wavelength for analysis of PCDD/Fs, the wavelength of the femtosecond laser utilized for multiphoton ionization was converted to near-ultraviolet status using stimulated Raman scattering. A femtosecond laser emitting at 300nm completely eliminated the background signal arising from the bleeding compounds generated from a stationary phase of the capillary column in GC. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2008.11.005

Language：English   Publishing type：Research paper (scientific journal)  

The quenching effect of a distributed feedback dye laser is detail studied. In detail a simulation model of combined dye lasers relying on the rate equation system with both lasers having a common lasing medium is demonstrated. The calculation using this model for a dye material shows that single picosecond pulses are attained for a quenched distributed feedback laser (Q/DFDL) over a large lasing range of dye materials, The simulation results using pyrromethene 567 dye provided single pulses of 49 ps with high narrowband as could possibily be approached.

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The use of two types of phase modulations arising from the coherent rotations of ortho-hydrogen and para-hydrogen to generate an intense ultrashort ultraviolet pulse without substantial generation of sub-pulses was demonstrated. This technique allows use of a high-energy long-probe pulse in the pump-probe regime for generating a high-energy compressed pulse. A 100-fs ultraviolet pulse was compressed to 11-fs by the phase modulation followed by dispersion compensation with chirped mirrors. (c) 2008 Optical Society of America.

DOI： 10.1364/OE.16.013492

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/chromsci/46.8.712

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Pentachlorodibenzofurans (pentaCDFs) are measured by means of gas chromatography combined with multiphoton ionization-mass spectrometry (GC-MPI-MS) using a picosecond Nd:YAG laser (266 nm) as an ionization source. In this study, the pre-treated sample was collected from flue gas in an incinerator. The pentaCDF isomers in the environment were determined, for the first time, by GC-MPI-MS. In addition, the details of the fragment patterns of mono-pentaCDFs were discussed, resulting in the detection of M(+)-COCl as a major fragment ion for all of them. On the other hand, the fragment peak of M(+)-Cl was quite small, suggesting that a molecular ion (e.g., tetraCDF(+)) can easily be identified without any interference by the M(+)-Cl fragment ion (e.g., pentaCDF(+)-Cl).

DOI： 10.1365/s10337-008-0648-9

Language：Japanese   Publishing type：Research paper (scientific journal)  

Generation of Continuous-Wave Highly-Repetitive Optical Pulse Trains by Molecular Modulation Mode-Locked Laser

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Transient stimulated rotational Raman scattering induced by a polarization-modulated femtosecond pulse whose polarization varies with time is reported. The peak intensity of the polarization-modulated pulse produced in this study is low compared to that of a pulse without polarization variation, and this leads to the low efficiency of self-phase-modulation and thus the high efficiency of stimulated Raman scattering compared to the case of a pump pulse without polarization modulation. The scattering process is unique in terms of the high peak ratio of the anti-Stokes to Stokes emissions compared to the ratio in the case of the scattering induced by linearly, circularly, and elliptically polarized pump pulses. Under optimum conditions, the ratio approaches 1, which is not realized in the general case of stimulated rotational Raman scattering.

DOI： 10.1103/PhysRevA.77.063802

Language：Others   Publishing type：Research paper (scientific journal)  

Stimulated rotational Raman scattering by a polarization-modulated femtosecond pulse

DOI： 10.1103/PhysRevA.77.063802

Language：English   Publishing type：Research paper (scientific journal)  

A narrow capillary, the tip of which was restricted to form a supersonic jet, was employed for sample introduction in time-of-flight mass spectrometry. The analyte was adsorbed at the tip of the capillary, due to a temperature decrease by the Joule-Thomson effect. Then, the analyte was desorbed using a pulsed laser emitting at 532 nm, and was entrained into a carrier gas. The analyte in the jet was subsequently ionized using a pulsed laser emitting at 266 nm. The duration of the analyte passing through the ionization region was 5.4 mm. in length (9 lis in time), and the signal intensity was enhanced 310-fold. This technique can also improve selectivity by controlling the nozzle temperature, since volatile compounds are not trapped at the tip of the capillary and then are not concentrated in the jet. In this approach, the analyte can be injected in a pulsed mode into a vacuum without using a complicated mechanical valve even at a repetition rate of > 1 kHz from the nozzle heated at a temperature of > 300 degrees C.

DOI： 10.1021/ac8000176

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

A highly efficient intracavity four-wave mixing in a Raman-active medium pumped by a continuous-wave laser is first demonstrated. Managing the intracavity dispersion to satisfy the phase matching in a high-finesse cavity substantially enhances the anti-Stokes emission. This process is observed in a region far beyond small signal approximation, indicating the generation of phase-locked sidebands arising from molecular modulation. This points to a novel approach of an optical modulator and mode-locked laser operating at a frequency of more than 10 THz.

DOI： 10.1103/PhysRevLett.100.073901

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

This study investigated a novel postcolumn reactor for fluorescence detection in CE. A laser-drilled capillary, with an aperture made by laser ablation, was used for mixing derivatization reagents with the analytes separated by CZE. The derivatization reagents, o-phthaldialdehyde (OPA), and 2-mercaptoethanol, were introduced into the capillary through the aperture and reacted with the analytes after CZE separation. High voltages were applied to both the inlet reservoir and the reservoir filled with the derivatization reagents. Thus, the flow rate of the derivatization reagents was controlled by the electric potential that was applied to the reservoir of the derivatization reagents. A UV light-emitting diode was used as an excitation light source for the fluorescence detection of OPA derivatives. A commercially available tee connector was compared with the laser-drilled capillary. The results implied that the dead volume of the laser-drilled capillary was less than that of the tee connector since the laser-drilled capillary suppressed band broadening more efficiently. The LODs for amino acids were determined to be similar to 5 mu M. The method was applied to the determination of amino acids in a Japanese beverage.

DOI： 10.1002/elps.200700274

Language：English   Publishing type：Research paper (scientific journal)  

A fluorescence lifetime imaging microscope (FLIM) was applied to study early-stage apoptotic cells stained with a SYTO13 dye. The fluorescence lifetime of SYTO13 in healthy cells was 3.8 +/- 0.3 ns but was reduced to 2.4 +/- 0.4 and 1.9 +/- 0.2 ns after a 3-h period of incubation with SYTO13 when doxorubicin, a known inducer of apoptosis, was added to human Ewing's family tumor cells at final concentrations of 250 and 500 nM, respectively, in a dose-dependent experiment. On the other hand, in a time-dependent experiment, the fluorescence lifetime decreased to 2.5 +/- 0.5 and 1.7 +/- 0.4 ns at a doxorubicin concentration of 750 nM after 2 and 4 h, respectively. A possible explanation for these results is self-quenching induced by a change in interprobe distance that arises from the condensation of DNA during apoptosis. In this study, the FLIM system was employed to investigate early-stage apoptosis that involves only small morphological changes, suggesting the potential advantage of this method for evaluating small biological effects in living cells. (C) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.ab.2007.04.032

Language：English   Publishing type：Research paper (scientific journal)  

The on-column capture of a specific protein using magnetic beads was applied to SDS-CGE. In a preliminary study, an immunological reaction in the presence of SDS, using a batch method, was attempted. Carbonic anhydrase (CA), alpha-lactalbumin (LA), and HSA were denatured by heating in the presence of SDS and 2-mercaptoethanol, and then reacted with anti-CA that had been immobilized on magnetic beads. Not only native CA, but also the denatured CA reacted with anti-CA, even in the presence of SDS. Therefore, the on-column capture of denatured CA separated by SDS-CGE was attempted using a two-point detection technique. A mixture of proteins, containing LA, CA, and HSA, were separated by SDS-CGE according to their M-Gamma. The CA was then specifically captured on anti-CA-immobilized magnetic beads, which were packed between two detection windows in the capillary column, during the electrophoresis. The results show that the technique leads to information similar to that obtained by Western blotting, i.e., a protein can be identified by its M-Gamma and reaction with its antibody.

DOI： 10.1002/elps.200600726

Language：English   Publishing type：Research paper (scientific journal)  

The temporal characterization of a femtosecond laser pulse in the deep ultraviolet region using an interferometric autocorrelation scheme is demonstrated. Two-photon ionization of a molecule in a time-of-flight mass spectrometer was used as a nonlinear detector to obtain an autocorrelation trace. This setup proved useful in not only providing a temporal characterization of a pulse but also investigating the ultrafast dynamics of photochemical processes. (C) 2007 Optical Society of America

DOI： 10.1364/OL.32.001716

Language：English   Publishing type：Research paper (scientific journal)  

We demonstrated that a 17.6 THz pulselike intensity modulation resulted from the coherent superposition of multifrequency continuous-wave emissions generated from a hydrogen-filled high-finesse cavity through a cascade-stimulated Raman scattering process. We pointed out that the complete phase-locked operation was hindered by the intracavity dispersion that caused nonequal separations between adjacent emission lines. (C) 2007 Optical Society of America.

DOI： 10.1364/JOSAB.24.001037

Language：English   Publishing type：Research paper (scientific journal)  

Laser emission, consisting of three primary colors, is generated by frequency conversions of the second-harmonic emission of a picosecond (120 ps) Nd:YAG laser by means of stimulated Raman scattering and subsequent four-wave Raman mixing in molecular deuterium. In the double-pass configuration, the fundamental beam (532 nm, 14.16 mJ, 100&#37;) is converted to blue (459 nm, 1.71 mJ, 12.1&#37;), green (532 nm, 7.04 mJ, 49.7&#37;), and red (632 nm, 4.90 mJ, 34.6&#37;), resulting in a total conversion efficiency of 96.4&#37;. (C) 2007 Optical Society of America.

DOI： 10.1364/AO.46.003001

Language：English   Publishing type：Research paper (scientific journal)  

The Hadamard transform (HT) technique, which permits the S/N in CE to be improved, was applied to MEKC. Multiple sample injection of fluorescent analytes according to a Hadamard code sequence was performed using an optically gated sample injection technique, in which a sample plug was produced based on photodegradation by irradiation with an intense laser beam. The capillary and reservoirs were filled with a sample solution containing buffer components and SDS as a pseudostationary phase. A preliminary study confirmed that fluorescein ion could be photobleached in the presence of SIDS. The optically gated sample injection technique was then applied to multiple sample injection, based on a Hadamard matrix. The S/N in the electropherogram obtained by HT-MEKC was improved substantially compared to that obtained by a single injection method. When the technique was applied to the separation of several amino acids labeled with FITC, the S/N ratio for each amino acid was enhanced, without any evidence of degradation in separation resolution. Moreover, HT-MEKC was applied to the analysis of amino acids contained in a Japanese beverage, resulting in improved S/Ns for the amino acids.

DOI： 10.1002/elps.200600183

Language：English   Publishing type：Research paper (scientific journal)  

Gas chromatography/multiphoton ionization/time-of-flight mass spectrometry (GC/MPI/TOF-MS) using a femtosecond laser source has been developed and applied to analysis of an authentic sample containing five polychlorinated dibenzofurans (PCDFs). The ionization efficiency was substantially improved for compounds such as tetrachlorinated dibenzofuran (tetraCDF) and pentachlorinated dibenzofuran (pentaCDF) using a femtosecond laser, instead of a nanosecond laser currently used for this purpose. The relatively poor efficiencies in nanosecond ionization can be attributed to the short lifetimes of the singlet excited states that are efficiently relaxed to triplet levels by intersystem crossing. The detection limits for pentaCDF isomers, i.e., 1,2,3,8,9-pentaCDF (non-toxic) and 1,2,3,7,8-pentaCDF (toxic), were determined to be ca. 100 pg, when the femtosecond laser was employed. The present method has the potential for use in the detection and determination of toxic PCDD/Fs in exhaust gas from an incinerator, because of the high inherent selectivity of GC and the high sensitivity of MPI/TOF-MS.

DOI： 10.2116/analsci.22.1483

Language：English   Publishing type：Research paper (scientific journal)  

The geometries and energies for the So and S, states of dibenzoftiran (DF) and all 135 PCDFs were obtained using Hartree-Fock (HF) and CI-Singles (CIS) methods. The transition energies determined from HF and CIS energies were corrected for electron correlation. If the electron correlation energies for the So and the S, state are calculated using a second-order Moller-Plesset perturbation (MP2) and a perturbative correction to CIS (termed CIS(D)) method, the S-1 <- S-0 0-0 transition energies are given with an error of 15.4-22.6&#37;. Electron correlation corrections to the transition energies were determined from a selected set of experimental transition energies on the assumption of the following additivity rule: the electron correlation energy of each state can be partitioned into contributions from the parent molecule and substituent chlormes. The transition energies after correction for electron correlation are in good agreement with available experimental data with an error of 0.2-3.5&#37;. The validity of the additivity rule with respect to electron correlation energy is discussed in relation to the geometry of the molecule. The findings show that the additivity rule holds within an error of 0.4&#37;. Vertical ionization potentials, which are useful in REMPI spectral studies, were calculated using Koopmans' theorem. The results confirmed that the S-1 <- S-0 origin transition energy is inversely proportional to the number of chlorine atoms tic, but the ionization potential is directly proportional to n(Cl). (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.theoshem.2006.07.005

Language：English   Publishing type：Research paper (scientific journal)  

An inverted microscope was combined with a compact dye laser with a pulse width of <190 ps and an intensified charge-coupled device (ICCD) camera with a minimum gate width of 200 ps. The resulting fluorescence lifetime imaging microscope, which has a temporal resolution of 340 ps, was used to measure the fluorescence lifetime of polymer microspherers. The results indicated a fluorescence lifetime of 0.9 ns. The present analytical instrument was also employed in an evaluation of biological cells after labeling them with SYTO 13, a fluorescent dye.

DOI： 10.2116/analsci.22.1291

Language：English   Publishing type：Research paper (scientific journal)  

The fluorescence lifetime of dibenzofuran and monochlorodibenzofuran was measured directly using a picosecond distributed-feedback dye laser and a fast-response microchannel-plate photomultiplier. The fluorescence lifetimes for dibenzofuran and monochlorodibenzofuran were determined to be 10.8 +/- 0.5ns and ca. I us, respectively, suggesting that the fluorescence quantum yield is reduced 10-fold by intersystem crossing induced by a chlorine atom in a dibenzofuran molecule. These findings highlight the advantages of a picosecond laser for the efficient multiphoton ionization of polychlorinated dibenzofurans. (c) 2006 Published by NIMS and Elsevier Ltd.

DOI： 10.1016/j.stam.2006.09.006

Language：English   Publishing type：Research paper (scientific journal)  

The development of an autocorrelator, using a photomultiplier as a nonlinear optical detector, for the measurement of a quasi-continuous-wave laser beam in the milliwatt range, is described. The contribution of the two-photon absorption relative to the one-photon absorption was investigated for the Sb-Cs photocathode used in the photomultiplier by means of the Z-scan method. This autocorrelator was applied to the measurement of the intensity of a laser beam sinusoidally modulated in the tetrahertz range. (c) 2006 Published by NIMS and Elsevier Ltd.

DOI： 10.1016/j.stam.2006.09.005

Language：English   Publishing type：Research paper (scientific journal)  

Geometries and S-1 <- S-0 origin transition energies for biphenyl, deuterated biphenyl, and 24 PCBs were obtained using a Hartree-Fock (HF), a single-excitation configuration interaction (CIS), and a related C1 method with doubles correction (CIS(D)). The HF and CIS geometries for biphenyl are in fairly good agreement with those obtained by a complete active space self-consistent field (CASSCF) method. Calculated results show that, in both S-0 and S-1 states of PCBs, the torsional angles and the inter-ring bond lengths can be classified according to the number of ortho-chlorine atoms, n(o-Cl). This suggests that the difference in electronic energy between the S-0 and the S-1 state also can be specified by n(o-cl). The HF and CIS energies were corrected for electron correlation on the assumption that the electron correlation energy can be partitioned into constituent contributions. Calculated S-1 <- S-0 origin transition energies agree with experimental values within an error of 2&#37;. This level of accuracy is comparable to that of the S-1 <- S-0 origin transition energy for biphenyl calculated using the CASSCF method. The correction for electron correlation energy is largely due to contributions of the parent molecule and ortho-chlorine atoms. The present results will facilitate the analysis of electronic spectra of PCBs. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.theochem.2006.06.009

Language：English   Publishing type：Research paper (scientific journal)  

The third harmonic emission (261 nm, 30 mu J) of a femtosecond Ti:sapphire laser is focused into molecular hydrogen to generate vibrational stimulated Raman emission. High-order emission lines are efficiently generated by using a high-beam-quality nearly-transform-limited laser and high-pressure hydrogen (40 atm) as a Raman medium. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2006.03.067

Language：English   Publishing type：Research paper (scientific journal)  

A method for capturing specific molecules separated by CE has been explored. To demonstrate on-column capture of migrating analyte molecules, two detection windows were fabricated on a capillary. Magnetic beads containing immobilized molecules that react with the specific molecules under study were placed between the detection windows in the capillary using magnets. Molecules in a sample solution injected into the capillary were separated and detected at the first detection window. After passing through the first detection window, the separated molecules encountered the magnetic beads, where the specific analyte was captured. As a result, the peak area for those analyte molecules decreased or disappeared completely at the second detection window. Rabbit IgG and carbonic anhydrase were employed to demonstrate on-column capture of a specific molecule. For rabbit IgG, magnetic beads containing the immobilized antibody (anti-rabbit IgG),were used. Rabbit IgG molecules were captured on the magnetic beads during CE migration. Furthermore, the capture of carbonic anhydrase was demonstrated by the reaction between magnetic beads (containing immobilized anti-rabbit IgG) and anti-carbonic anhydrase (rabbit IgG), before the beads were packed in the capillary. After packing the magnetic beads in the capillary, a mixture of two proteins was injected into the capillary. Two proteins were detected at the first detection window, while the peak corresponding to carbonic anhydrase disappeared at the second detection window. The results show that using an appropriate antibody, the present technique would be applicable to any proteins.

DOI： 10.1002/elps.200500936

Language：English   Publishing type：Research paper (scientific journal)  

A novel method for compressing a laser pulse, using a combination of transient stimulated Raman scattering and a pump-probe technique, is proposed. The approach does not require a short laser pulse, in contrast to a reported method based on impulsive stimulated Raman scattering. The observed spectrum was sufficiently broad to generate a sub-10 fs pulse. In fact, a 100-fs pulse in the near-ultraviolet region was compressed to the sub-30 fs. Further compression of the laser pulse would be achieved by compensating for phase distortion, as suggested from the observed data of the spectral phase. (c) 2006 Optical Society of America.

DOI： 10.1364/OE.14.003083

Language：English   Publishing type：Research paper (scientific journal)  

A hydrophilic polymer, poly(vinylpyrrolidone) (PVP), was employed for suppressing the electroosmotic flow (EOF). A capillary was filled with aqueous PVP solution for coating the capillary wall with PVP; the PVP solution was then replaced by a migration buffer solution containing no PVP. Three types of PVP with different molecular weights were examined. The EOF was suppressed more effectively as the molecular weight of PVP increased. The EOF in the coated capillary was similar to 10-fold smaller than that of a bare capillary and was constant in the pH range of 6-8. The suppressed EOF was stable even when no PVP was added to the migration buffer. However, the EOF increased significantly when sodium dodecyl sulfate was added into the migration buffer. The method was applied for determining the electrophoretic mobilities of inorganic anions that have negative electrophoretic mobilities larger than the electroosmotic mobility of the bare capillary. A novel method for determining the electrophoretic mobilities was proposed based on the linear relationship between electric current and electrophoretic mobility. The electrophoretic mobility was proportional to the electric current. Therefore, the intercept of the regression equation represents the electrophoretic mobility at room temperature. The electrophoretic mobilities were in good agreement with the absolute electrophoretic mobilities. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2005.08.062

Language：English   Publishing type：Research paper (scientific journal)  

An ultrafast light-intensity modulator, based on stimulated Raman scattering, is described. The intensity of a continuous wave laser is fully modulated at 17 THz using hydrogen in a high-finesse cavity. The modulation frequency is determined by the molecular constant of the Raman medium, i.e., the Raman shift frequency. The modulation frequency can be changed in the tetrahertz range by replacing the Raman medium. Due to the accurate modulation frequency and the high beam coherence, this device is amenable to a variety of applications such as in basic science and also in advanced industrial technology. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2174091

Language：English   Publishing type：Research paper (scientific journal)  

Hadamard transform capillary electrophoresis (HTCE) based on electrokinetic injection allows laser-induced fluorescence detection using a small laser, namely the laser-diode-pumped YAG laser, as an excitation source. A small hole is fabricated at the center of a capillary by laser ablation; this hole functions as an inlet port for a sample solution. Therefore, the sample solution can be introduced electrophoretically into the capillary through the small hole. Multiple sample injection is accomplished by introducing a buffer solution from the end of the capillary and the sample solution through the hole. Both solutions are injected using two sets of high-voltage power supplies and migrate toward the opposite end of the capillary. A fluorescent analyte, rhodamine B, is successfully detected in the case of both single and multiple injection according to the Hadamard sequence code. By transforming the data encoded by the Hadamard matrix, the decoded data showed an increase in the signal-to-noise (S/N) ratio by a factor of 9.8. In the case of the sample containing two amino acids labeled with rhodamine B isothiocyanate (RBITC), although the concentration of every component including free RBITC is lower than the concentration limit of detection obtained by single injection, a substantial improvement in the sensitivity is achieved and all components are identified by the Hadamard transform technique. (c) 2005 Elsevier B.V. All fights reserved.

DOI： 10.1016/j.aca.2005.06.068

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The generation mechanism of stimulated Raman scattering (SRS) in a gaseous medium pumped by a pulse with a duration close to one rotational period of molecular motion was studied. We found that the self-seeding effect caused by nonlinear pulse reshaping during propagation of a pump pulse was essential for the excitation of Raman coherence. This clearly explains the selective excitation of specific motions of molecules and the substantial reduction of the threshold of SRS generation. (c) 2005 Optical Society of America

DOI： 10.1364/JOSAB.22.002642

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The development of a distributed-feedback dye laser, with a pulse width and a line width of 25 ps and 8.78 pm, respectively, is described. Using this nearly Fourier-transform-limited pulse, we measured the first singlet-excited-state lifetime of 1,2,4-trichlorobenzene. The tunable picosecond dye laser developed herein has a potential for the lifetime measurement and the efficient multiphoton ionization of aromatic hydrocarbons with a larger number of chlorine atoms and shorter excited-state lifetimes.

DOI： 10.2116/analsci.21.693

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The development of an autocorrelator based on a two-photon absorption of a photomultiplier photocathode is described. A solar-blind photomultiplier, sensitive in the far-ultraviolet region, is used to detect a two-photon absorption in the near-ultraviolet region. Such an autocorrelator can be used to measure the pulsewidth of a laser (396 nm, 110 fs) produced by the second harmonic generation of a Ti:sapphire laser. (C) 2005 American Institute of Physics.

DOI： 10.1063/1.1850631

Language：English   Publishing type：Research paper (scientific journal)  

An on-column immunological reaction was employed to achieve simple and rapid analysis in an immunoassay based on capillary electrophoresis using semiconductor laser-induced fluorescence detection. Human serum albumin (HSA) labeled with sulfoindocyanine succinimidyl ester (Cy5), a fluorescent compound with an absorption maximum at 649 urn, was used as a fluorescent probe for the immunoassay. In a binding assay, with anti-HSA as the analyte molecule, Cy5-HSA was injected in a capillary column followed by the injection of anti-HSA so as to form individual zones. By applying a potential, the anti-HSA reacted with Cy5-HSA at the boundary between Cy5-HSA and anti-HSA zones, since anti-HSA has a higher electrophoretic mobility than Cy5-HSA. Furthermore, the on-column method enhances the sensitivity by injecting a large volume of the sample. Free Cy5-HSA and its immunocomplex with anti-HSA were separated with less degradation in resolution than that predicted from the injection time of anti-HSA, even when the injection time for anti-HSA was increased. The ratio of the peak area of the complex to that of the total Cy5-HSA (free Cy5-HSA and the complex) increased in proportion to the injection time of anti-HSA. As a result, the detection limit was improved up to eight-fold (the concentration detection limit, 0.007 mg mL(-1)), for an injection time of 240 s, compared to that obtained using an off-column sample preparation. Furthermore, the on-column reaction method was applicable to an immunoassay to determine native HSA, in which native HSA and Cy5-HSA react with anti-HSA stepwise. The detection limit in the stepwise reaction immunoassay was 0.005 mg mL(-1), which is 14 times lower than that in an off-column method, with the analysis time less than 10 min as the result of increasing the injection time of native HSA. In addition, the present on-column immunoassay was applied to the sample containing a high concentration of salts for investigating the effect of salts in the sample solution. (C) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2005.01.037

Language：English   Publishing type：Research paper (scientific journal)  

It was confirmed that both quadrupole moments and polarizabilities of polychlorinated dibenzofurans (PCDFs), which were calculated using Hartree-Fock theory and/or density functional theory, change systematically with the chlorination pattern governing molecular charge distribution. A mathematical model based on ligand-receptor binding and solute-solvent interaction is reported to explain the difference in toxicity between PCDFs. Multiple regression analysis demonstrated that the difference in the potency of aryl hydrocarbon hydroxylase (AHH) and 7-ethoxyresorufln O-deethylase (EROD) inductions is mostly determined by the polarizabilities of PCDFs. This suggests that the interaction of a PCDF with the aryl hydrocarbon receptor (AhR) and its interaction with surrounding molecules in the cytosol are dispersion interactions rather than electrostatic interactions. Quadrupole moment, electron affinity, and absolute hardness do not appear to be significantly correlated with the differences in AHH and EROD activities among PCDFs. The entropy change of dissolution is important in predicting the AHH and EROD activities with good accuracy. A mathematical model is also used to study the differences in AhR binding between PCDFs.

DOI： 10.1021/tx049874f

Language：English   Publishing type：Research paper (scientific journal)  

A novel method for the on-column sample stacking of proteins is described. The strategy takes advantage of interactions between protein molecules and sodium dodecyl sulfate (SDS) monomers. A long plug of a protein sample (either acidic or basic) is injected into a capillary filled with a background electrolyte (BGE) containing SDS. When a potential is applied, the proteins interact with SDS monomers in the BGE to form protein-SDS complexes that migrate more slowly than the corresponding uncomplexed protein, resulting in protein stacking. Both acidic and basic proteins migrate at an almost identical electrophoretic velocity after stacking, which indicates that the protein-SDS complexes formed in the BGE zone have a similar charge/mass ratio. The mechanism of stacking was investigated using a sample consisting of a basic protein, lysozyme, and a small molecule, methylene blue. The findings clearly show that two interactions with SDS occur, a stepwise binding interaction between protein molecules and SDS monomers and an interaction in which the small molecules enter into micelles formed by SDS molecules. The method was also applied to the detection of a protein labeled with a fluorescent labeling reagent at trace levels. The labeled protein was detected even under labeling conditions where the labeling efficiency was too low to detect by short-plug injection.

DOI： 10.2116/analsci.21.37

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (other academic)  

Self-Compression of an Ultraviolet Optical Assisted by Raman Coherence Induced in the Transient Regime

Language：English   Publishing type：Research paper (international conference proceedings)  

Development of A Sensitive Autocorrelator in the Ultraviolet and Near-Infrared Region

Language：English   Publishing type：Research paper (international conference proceedings)  

Spectral Broadening and Temporal Reshaping of A Femtosecond Laser Pulse Due to a Nonlinear Optical Interaction in A Hydrogen Gas

Language：English   Publishing type：Research paper (scientific journal)  

To attempt to expand the spectral domain for pulse shortening, we generated several emission lines by stimulated Raman scattering and subsequent four-wave Raman mixing. The efficiency of generation of the Raman emission was improved by passing the beam through two Raman cells that were connected in series. The group-velocity dispersion induced by a Raman cell window and hydrogen was compensated for by means of a pair of chirped mirrors for pulse compression. By a phase lock of the emission lines in the process of four-wave Raman mixing, the pulse width was reduced from 114 to 17 fs in the second Raman cell. (C) 2004 Optical Society of America.

DOI： 10.1364/OL.29.002809

Language：English   Publishing type：Research paper (scientific journal)  

The development of a tunable picosecond dye laser, based on quenching cavity (QC) in an oscillator and spectro-temporal selection (STS) before amplification, is described. A theoretical model was constructed for the calculation of temporal and spectral evolutions of dye laser emission using a series of equations representing population inversions. The pulsewidth, linewidth, and pulse energy, obtained experimentally, were 90 ps, 0.2 nm, and 10 muJ, respectively. The tunable range, in which a single picosecond pulse can be obtained, was expanded from 4 to 20 nm for a single dye solution by applying QC to STS. Thus, the spectral region was covered from 320 to 360 nm using two laser dyes, i.e., BM-terphenyl and BBQ. Experimental data obtained using the instrument were in reasonably good agreement with values predicted from theory.

DOI： 10.1007/s00340-004-1591-6

Language：English   Publishing type：Research paper (scientific journal)  

We have observed self-modulation and self-compression of a femtosecond laser pulse after passing the beam through a Raman-active medium of hydrogen. Femtosecond pulses produce Stokes emissions of ortho-hydrogen and para-hydrogen, depending on the input beam conditions. The shape of the output pulses drastically changed as a function of the intensity of the Stokes emissions and the total width of the spectrum. This is attributed to nonlinear modulation of the wave form induced by coherent rotational motions of hydrogen molecules in the time domain.

DOI： 10.1103/PhysRevA.70.031801

Language：English   Publishing type：Research paper (scientific journal)  

Polychlorinated biphenyls (PCBs), used as a heat exchange oil (Kanechlor, KC-300), can be measured by gas chromatography combined with multiphoton ionization mass spectrometry (GC/MPI-MS). Several compounds, e.g., 4,4'-dichlorobiphenyl and 3,4,4'-trichlorobiphenyl, have nearly the same retention time but can be selectively determined by MPI-MS. Coplanar PCBs are more efficiently ionized using the fourth harmonic emission of a Nd:YAG laser (266 nm), compared to noncoplanar PCBs. Thus, the approach reported herein may be useful in the selective as well as the sensitive analysis of toxic PCBs, contained in old transformers and capacitors that have been mandated by the government to be properly disposed of within 10 years in Japan.

DOI： 10.1021/ac049496j

Language：English   Publishing type：Research paper (scientific journal)  

A novel injection device for applying absorption spectrometty to Hadamard transform (HT) capillary electrophoresis is described. A small hole, at the center part of the capillary, functions as an inlet port for the sample. The hole is immersed in a sample solution and the end of the capillary that is usually employed for sample introduction is immersed in a buffer solution. An ultraviolet absorption detector is placed between the sample injection port and the other end of the capillary filled with a buffer solution. A high potential is continuously applied between the injection port and the end of the capillary, which allows the sample solution to be introduced into the separation capillary. By application of a higher potential modulated according to a Hadamard code between both ends of the capillary, the buffer solution is injected into the separation capillary. In some preliminary experiments, this injection device was utilized to introduce a single sample segment into a capillary. As expected, a single peak was observed in the electropherogram for a sample containing a single component. This device was then employed for multiple sample injection in HT capillary electrophoresis. An 8-fold improvement in the S/N ratio was observed when the HT technique was used, in which a 255-order of a Hadamard matrix was used, as expected from theory. The present approach was also utilized for the sensitive detection of a sample comprised of multiple components.

DOI： 10.1021/ac035366j

Language：English   Publishing type：Research paper (scientific journal)  

A circularly, elliptically, or linearly polarized beam of a Nd:YAG laser emitting at 532 nm is focused into molecular deuterium (D-2), generating a rotational stimulated Raman emission. By decreasing the temperature to 77 K, the S-0(2) transition, which has a Raman shift frequency of 415 cm(-1) is completely suppressed and the S-0(0) transition having a shift frequency of 179 cm(-1) is efficiently generated from ortho-D-2. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optcom.2004.03.083

Language：English  

A two-color three-photon ionization scheme, for the efficient and selective ionization of a chlorinated aromatic hydrocarbon that has an ionization potential higher than the two-photon energy of the laser used for excitation, is described. In this technique, an ultraviolet (UV) laser, i.e., the second harmonic emission of a fundamental (VIS) laser, is used for excitation and a UV and VIS laser for the subsequent two-photon ionization from the electronic excited state. A sample of o-chlorophenol was used as a model compound to demonstrate the advantage of this technique. The signal in supersonic jet/resonance-enhanced multiphoton ionization/mass spectrometry was increased similar to4 times by the introduction of the VIS beam, when the polarization was adjusted to be parallel to the UV beam. Thus, the two-color three-photon (2UV+VIS) ionization scheme is more sensitive than one-color three-photon (3UV) ionization. The merits of this method over other ionization schemes such as two-color two-photon (UV1 + UV2) ionization are discussed in terms of sensitivity and selectivity in spectrometric analysis.

DOI： 10.1021/ac0350571

Language：English   Publishing type：Research paper (scientific journal)  

When a 100-fs Ti:sapphire laser is focused into molecular deuterium cooled at 77 K, rotational stimulated Raman emission is generated based on four-wave Raman mixing. By phase locking the emission lines, the laser pulsewidth was reduced to 40 fs, when a nearly transform-limited pulse was utilized as a fundamental laser. The pulsewidth was further reduced to 20 fs, when a positively chirped pulse was employed. Computer simulation suggests that the Raman emission is strongly chirped and a train of pulses with lower intensities are formed when a chirp pulse is used as a fundamental laser.

DOI： 10.1007/s00340-004-1468-8

Language：English   Publishing type：Research paper (scientific journal)  

The emission lines generated by four-wave Raman mixing were coherently phased and provided an similar to30-fs pulse without any loss of energy simply by passage of the pulse beam through molecular hydrogen. (C) 2004 Optical Society of America.

DOI： 10.1364/OL.29.000400

Language：English  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Application of Hadamard Transformation to Chiral Separation by Capillary Electophoresis

Language：English   Publishing type：Research paper (scientific journal)  

A concentration detection limit of 100 fM was achieved for the fluorescein ion by improving the experimental setup used for Hadamard transform capillary electrophoresis. Two argon-ion lasers, a gating laser for sample injection and a probe laser for the excitation of analyte molecules, were employed for the efficient photodegradation of analyte molecules in laser-induced fluorescence detection using an optically gated sample-injection method. In addition, a dichroic mirror, located in the pathway of the probe laser was used to exclude the other lines of the argon-ion laser. Using a Hadamard matrix on the order of 2046, the concentration limit of detection for fluorescein ion was determined to be 100 fM at S/N = 3, in which the average number of molecules in a single injection volume was calculated to be 27. The influences of the output power in both the gating and probe lasers on the sensitivity are also discussed.

DOI： 10.2116/analsci.19.1659

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/S0030-4018(03)01675-4

Language：English   Publishing type：Research paper (scientific journal)  

Picosecond and femtosecond lasers having different pulsewidths were employed for the generation of multi-color laser emission via stimulated Raman scattering and four-wave Raman mixing using a KGd(WO4)(2) crystal. Seven emission lines, consisting of high-order Stokes and anti-Stokes emissions, were observed at a laser pulsewidth of 20 ps and a pulse energy of 70 muJ. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0030-4018(03)01675-4

Language：English   Publishing type：Research paper (scientific journal)  

A novel diffractive optical element was constructed by means of gel electrophoresis. Five capillaries were filled with a methylene blue solution and inserted into a slab gel. An electrical potential was then applied to the slab gel. Methylene Blue in the capillaries underwent electrophoretic migration, forming clear blue bands in the gel. The bands functioned as a transmission grating, and diffracted a laser beam. The intensity of the diffracted light increased with increasing the concentration of methylene blue.

DOI： 10.2116/analsci.19.795

Language：English   Publishing type：Research paper (scientific journal)  

The effect of solvent on the solution inlet/laser vaporization technique for multiphoton ionization/time-of-flight mass spectrometry (MPI/TOF-MS) was examined. In this technique, a sample of dibenzofuran, dissolved in an organic solvent, is introduced underneath the nozzle for jet expansion through a narrow capillary, at the end of which a glass frit is formed to vaporize the solvent and to deposit the analyte for laser vaporization. The ion signal, consisting of irregular peaks, is increased by the introduction of a laser pulse for vaporization, when methanol is used as a solvent. This can be attributed to local boiling of the solution at the surface of the frit due to the volatile nature of methanol. When glycerin was added to the methanol, the irregular peaks were substantially decreased. However, an increase in signal intensity was not observed by laser vaporization when the glycerin content was increased to 50&#37;. In the case of n-nonane, which is currently used as a solvent for dissolving dioxin standards, no irregular peaks were observed and the signal intensity was increased by laser vaponzation. (C) 2003 Elsevier Science B.V All rights reserved.

DOI： 10.1016/S0003-2670(03)00345-3

Language：English   Publishing type：Research paper (scientific journal)  

A tunable narrow-band picosecond dye laser emitting in the ultraviolet region was amplified using a Ce:LiCaAlF6 crystal pumped by the fourth-harmonic emission of a Nd:Y3Al5O12 laser. The single-pass gain obtained exceeded 2 in the spectral range of 288 to 297 nm. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1576294

Language：English   Publishing type：Research paper (scientific journal)  

Mono-, di- and trichlorophenols were measured using resonance-enhanced multiphoton ionization mass spectrometry (MPI-MS) combined with supersonic jet (SSJ) or effusive molecular beam (EMB) spectrometry. All mono- and dichlorophenols, except 2,6-dichlorophenol, provided sharp and structured MPI spectra for the S-1<--S-0 transition. Selectivity and sensitivity were both enhanced when SSJ spectrometry was used, compared with EMB spectrometry, because of a narrower linewidth in the MPI spectrum, given by molecular cooling by supersonic jet expansion. The ionization efficiency decreased with increasing number of chlorine substitutents for the chlorophenols, since they have shorter excited-state lifetimes and require three photons for ionization. Some of the chlorophenols, which are toxic themselves, have the potential for use as indicators for analysis of polychlorinated dibenzo-p-dioxin/dibenzofurans in flue gases emitted from an incinerator.

DOI： 10.1366/00037020360626014

Language：English   Publishing type：Research paper (scientific journal)  

The application of a Hadamard transform technique to microchip electrophoresis is described. The sample is electrokinetically injected into a separation channel and is then detected by diode laser-induced fluorometry. The sample and buffer solutions are introduced into the channel by controlling the high voltages applied to the solutions, according to a code determined by a Hadamard matrix. The S/N ratio of the signal in the electropherogram can be improved by a factor of 5 in comparison with that obtained by a conventional single-injection method, although an 8-fold improvement is theoretically predicted when a 255-order matrix is used.

DOI： 10.1021/ac026330e

Language：English   Publishing type：Research paper (scientific journal)  

Two-color (1+1') resonance-enhanced multiphoton ionization/time-of-flight mass spectrometry (REMPI/TOF-MS) combined with supersonic jet (SSJ) spectrometry has been demonstrated. The methodology uses a two-color laser beam consisting of a Stokes beam generated by stimulated Raman scattering (SRS) and a fundamental beam for the excitation and subsequent ionization of p-dichlorobenzene. The MPI signal was found to be substantially increased when a two-color laser beam was employed. This approach greatly simplifies the analytical system and reduces the cost of the instrumentation required for two-color ionization. The potential advantage of applying this method for the analysis of polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) emitted from an incinerator is discussed.

DOI： 10.2116/analsci.19.387

Language：English   Publishing type：Research paper (scientific journal)  

Development of a compact supersonic jet/multiphoton ionization/time-of-flight mass spectrometer for the on-site analysis of dioxin, part II: Application to chlorobenzene and dibenzofuran
A compact supersonic jet/multiphoton ionization/mass spectrometer (SSJ/MPI/MS) equipped with a single pump system was developed for use in the analysis of dioxin. A mass spectrum and multiphoton ionization spectrum were obtained for chlorobenzene and dibenzofuran using an optical parametric oscillator (OPO) for excitation and subsequent ionization. The detection limit for chlorobenzene (S/N = 3) was 0.3 ppb, which corresponds to an absolute amount of 0.1 pg. The rotational temperature was 35 K. This slightly high temperature can be attributed to the long nozzle throat used in the instrument.

DOI： 10.2116/analsci.19.383

Language：English   Publishing type：Research paper (scientific journal)  

A new type of compact supersonic jet/resonance-enhanced multiphoton ionization/time-of-flight mass spectrometer is described. The analytical instrument, consisting of a single turbo molecular pump equipped with a rotary pump, was maintained at < 2 x 10(-3) Pa when a 0.3-atm sample was injected into a vacuum at 10-Hz using a 200-mus pulse valve. The diameters of the extraction and ground skimmer electrodes were expanded to 30 mm in order to avoid strong focusing and defocusing of the ion, and the optimum conditions for the system were investigated. The mass spectrometer functioned as expected: (1) no defocusing of the ion beam was observed even when the potential of the einzel lens was adjusted to zero; (2) the direction of the ion beam to an assembly of microchannel plates deviated in the expected manner when the potential of the defection electrode was changed from 0 to 30 V.

DOI： 10.2116/analsci.19.379

Language：English   Publishing type：Research paper (scientific journal)  

A new sample introduction technique for ensuring the safety of a researcher during the measurement of hazardous compounds, such as dioxins, by supersonic jet spectrometry is described. The solution containing the analyte is introduced beneath the nozzle through a narrow capillary with a glass frit at the end, which is formed to vaporize only the solvent and to deposit the analyte. The first laser, that is, the second harmonic emission of a Nd: YAG laser, vaporizes the analyte and entrains it into a supersonic jet. The analyte molecule is ionized by the second laser, that is, an optical parametric oscillator. Ion measurement is achieved by a time-of-flight mass spectrometer. The analyte molecule is localized in the jet, thus permitting the amount of sample to be minimized. The minimum amount of phenol necessary for measurement of a multiphoton ionization spectrum by scanning the wavelength of the ionization laser in the 3-nm range was 180 pg, which is similar to or slightly less than the tolerable daily intake (TDI) of dioxin.

DOI： 10.1021/ac025843i

Language：English   Publishing type：Research paper (scientific journal)  

A new design and the characteristics of operating a distributed-feedback dye laser (DFDL) pumped by the fourth-harmonic emission of a Q-switched Nd:YAG laser are described. An ultraviolet nearly transform-limited picosecond pulse was generated by means of two right-angle prisms in the pumping geometry, and the laser wavelength was continuously tunable from 318 to 369 nm using two dye solutions (BM-terphenyl and BMQ). The application of this DFDL to the lifetime measurement of a fluorescent dye is also presented. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1529298

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1366/000370202760295511

Language：English   Publishing type：Research paper (scientific journal)  

Characteristic hard X-rays emitted from a laser-produced plasma induced by focusing a femtosecond KrF laser pulse are employed for elemental analysis. The emission spectrum of the hard X-ray arising from a stainless steel sample is measured by means of a single-photon-counting X-ray detector equipped with a multichannel analyzer. The elemental analysis is carried out from the photon energy of the Kalpha. line observed in the X-ray emission spectrum, and a calibration curve is constructed for Fe using stainless steel samples prepared at different concentrations (SUS-301, 310, and 316). A continuum band was overlapped on the sharp Kalpha lines in the Xray spectrum, which made the assignment of the weak characteristic Kalpha lines arising from minor elements difficult. In order to suppress this undesirable emission, a prepulse technique was employed. The continuum emission was shifted toward lower energies, and, as a result, the characteristic Kalpha lines were more clearly observable. The potential advantages of the present approach are also discussed in this study.

DOI： 10.1366/000370202760295395

Language：English   Publishing type：Research paper (scientific journal)  

The degree of labeling, i.e., dye/protein ratio (DIP) is important for characterizing properties of dye labeling with proteins. A method for the determination of this ratio between a fluorescent cyanine dye and bovine serum albumin (BSA), based on the separation of the labeling mixture using micellar electrokinetic chromatography with diode laser-induced fluorescence detection, is described. Two methods for the determination of DIP were examined in this study. In these methods, a hydrolysis product and impurities, which are usually unfavorable compounds that are best excluded for protein analysis, were utilized to determine the amounts of dye bound to BSA. One is a direct method in which a ratio of the peak area of BSA to the total peak area of all the products produced in the labeling reaction was used for determining the average number of dye molecules bound to a single BSA molecule. The other is an indirect determination, which is based on diminution of all peak areas related to the products except for the labeled BSA. These methods were directly compared by means of a spectrophotometric method. The experimental results show that the indirect method is both reliable and sensitive. Therefore, DIP values can be determined at trace levels using the indirect method.

DOI： 10.1002/1522-2683(200208)23:15<2465::AID-ELPS2465>3.0.CO;2-G

Language：English   Publishing type：Research paper (scientific journal)  

When a labeling reagent is used, in the determination of proteins by capillary electrophoresis with laser-induced fluorescence detection, the multiple labeling of proteins frequently occurs, which can degrade the separation efficiency. In order to understand the influence of the multiple labeling of proteins on separation efficiency, the band broadening caused by a labeling reaction between bovine serum albumin (BSA) and a cyanine fluorescent dye (Cy5) was investigated using micellar electrokinetic chromatography in conjunction with diode laser-induced fluorometry. With the aid of an internal standard, methylene blue, the height equivalent to the theoretical plate (HETP) ratio of BSA to methylene blue was used as an indicator for band broadening under optimum separation conditions. Labeling conditions, including reaction buffer pH, reaction time, and initial concentration of Cy5 to bovine serum albumin, were found to influence the HETP ratio. The separation efficiency for the labeled protein was degraded by experimental conditions employed in the labeling, which indicates an increase in the heterogeneity of the final products. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0021-9673(02)00357-6

Language：English   Publishing type：Research paper (scientific journal)  

We report on the generation of a background-free nearly transform-limited picosecond pulse using a simple quenching scheme in a distributed feedback dye laser. The pulsewidth and spectral linewidth were 65 ps and 10 pm, respectively. The product of these values is 0.650, which is close to the transform limit of 0.441 for a Gaussian pulse. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1470242

Language：English   Publishing type：Research paper (scientific journal)  

The design and construction of a new type of time-of-flight mass spectrometer is described. The instrument was designed to improve the ionization efficiency and to efficiently detect ions. The system performance was evaluated using the SIMION software, and was compared with the experimental results. The shapes of the repeller, extraction, and ground electrodes had a strong effect on the trajectory of ions in the processes of ion acceleration and focusing. The major difference between the theory and the experiment can be attributed to space-charge effects.

DOI： 10.2116/analsci.18.567

Language：English   Publishing type：Research paper (scientific journal)  

Hadamard transform capillary electrophoresis, which is based on a multiple sample injection technique, was combined with laser-induced fluorometry and utilized in the determination of analytes at subpicomolar levels. The sensitivity was substantially improved by increasing the order, i.e., the number of elements, of the Hadamard matrix. In facts the signal-to-noise ratio was enhanced 18-fold by the use of a matrix of order 2047. A feasibility study was carried out by computer simulation to study the detection of an average of less than a single molecule in a single injection volume. The signal peak was clearly observable even under conditions at which only 0.3 molecule is present in the volume. Thus, this approach is potentially useful for ultratrace analysis, in which conventional single-injection capillary electrophoresis cannot be applied.

DOI： 10.1021/ac011149b

Language：English   Publishing type：Research paper (scientific journal)  

A four-pass cell was employed for the multifrequency parametric Raman generation in gaseous hydrogen. More than 18 rotational-vibrational Raman lines from 450 to 830 nm were generated using an 80-mJ, 3-ns pump pulse at a wavelength of 532 nm. The output spectrum broadening was observed by increasing the number of passes of the pump pulse through the Raman cell. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1468686

Language：English   Publishing type：Research paper (scientific journal)  

The rotational parametric Raman scattering of hydrogen in a cell 0.6 m in length was examined using a variable diameter of collimated pump beam. At decreasing diffraction length of the pump beam from 330 to 95 cm, the energy of anti-Stokes components was reduced by a factor of more than 20. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0030-4018(02)01204-X

Language：English   Publishing type：Research paper (scientific journal)  

A distributed-feedback dye laser with a quenching cavity was designed and constructed for generating a tunable picosecond pulse with a narrow spectral linewidth. This nearly transform-limited pulse was succeedingly amplified by a triple-pass off-axis amplifier. The pulse duration and the spectral linewidth were 60 ps and 9.4 pm, respectively. The amplified pulse was frequency-doubled by second-harmonic generation, producing a 0.5-mJ pulse with no background emission. The potential advantage of this laser in the analysis of dioxin based on supersonic jet/resonance-enhanced multiphoton ionization/mass spectrometry is discussed.

DOI： 10.2116/analsci.18.243

Language：English   Publishing type：Research paper (scientific journal)  

We describe the use of micellar electrokinetic chromatography with diode laser-induced fluorometry (MEKC-DLIF) as a tool to characterize a labeling reaction between sulfoindocyanine succinimidyl ester (Cy5), a cyanine fluorescent dye, and a model protein, bovine serum albumin (BSA). To decrease the influence of imprecise injection, methylene blue was added as an internal standard. Labeled BSA was completely separated from the unconjugated Cy5, and methylene blue under optimized conditions. A kinetic study of the reaction was performed by changing some parameters, such as reaction buffer pH, reaction buffer concentration and the initial concentration of BSA. A comparison between the current method and traditional methods was made.

DOI： 10.1002/1522-2683(200202)23:4<550::AID-ELPS550>3.0.CO;2-F

Language：English   Publishing type：Research paper (scientific journal)  

The development of an optical channel, a new analytical technique for evaluating the elasticity of biological cells, is described in this study. Two types of erythrocyte cells, i.e., young and old cells, were examined via their introduction into a flowing medium, to which a laser beam was focused in the opposite direction. An erythrocyte cell is trapped in a laser beam by a gradient force, moves in the downstream direction, and is then elongated at the beam waist. The change in shape was measured directly using a microscope equipped with a charge-coupled-device camera. It is probable the main driving force for the cell deformation is a shear stress generated by a medium flow, since an estimate of the gradient force suggests that it is too small to change the shape of an erythrocyte. The average values of the elongation of young and old cells were 2.4 +/- 0.6 and 2.1 +/- 0.5, respectively. These values are in reasonably good agreement with values obtained using a rheoscope method. The deformation was measured without any physical contact to the solid surface, and therefore, damage to cells such as these are minimal.

DOI： 10.1021/ac010441g

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Phosphor materials that were manufactured for use in a plasma display panel (PDP) were investigated by employing a newly designed time-resolved vacuum-ultraviolet (VUV) spectrometer, which consists of a pulsed VUV laser and a fast photodetector. The VUV spectrometer was used to collect quantum efficiency data as well as the rise and decay times for the PDP phosphor luminescence. Both the rise and decay times increased with decreasing excitation wavelength in the VUV region. This result can be explained by a change in the mechanisms of photoexcitation and luminescence, that is, from charge-transfer excitation to host-lattice excitation below 200 mn. The present instrument was also used for an evaluation of the phosphor materials (Bal(1-x)MgAl(10)O(17):Eu-x(2+)) by changing the Eu2+ concentration. The obtained data suggest that the impurities and defects are located inside the host crystal. Thus, the VUV spectrometer constructed in this study has considerable potential for use in investigating the nature of PDP phosphor materials.

DOI： 10.1021/ac010162t

Language：English   Publishing type：Research paper (scientific journal)  

An extremely long train of highly repetitive pulse (17 THz) is obtained by the rotational four-wave Raman mixing of molecular hydrogen in a resonator using a computer simulation. This highly repetitive pulse can be obtained only when the laser wavelength and the resonator are adjusted to specified values. This pulse train has potential for use in ultrafast data communication because of the accurately determined repetition rate or even as a frequency standard, since the frequencies of the emission lines can be stabilized and locked to the above values.

Language：English   Publishing type：Research paper (scientific journal)  

Optimized geometries and total energies for the So and S, states of five monochlorophenols and phenol were calculated using a 10-electron, 8-orbital CASSCF/6-31G(d). We investigated the effects of a substituent chlorine atom and the S-1 <-- S-0 excitation on the geometries and charge distributions. It is common to all monochlorophenols that the substituent chlorine atom makes the C-O bond shorten and that an empirical rule with respect to the internal ring angle concerned with the substituent chlorine atom holds true. The S-1 <-- S-0 excitation enlarges the carbon ring and reduces the C-H, C-O, and C-CI bond lengths. The O-H bond length and the C-O-H bond angle are almost invariant upon excitation. A structural approach based on van der Waals radii has clarified that cis-o-chlorophenol has a hydrogen bond in the S-1 state and that the interaction between the chlorine and oxygen atoms in a trans-o-chlorophenol affects its geometries for the S-0 and S-1 states. As to the origin energies of the S-1 <-- S-0 transitions, the present method can compete in terms of accuracy with a 8-electron, 7-orbital CASSCF/6-31G(d,p). The increasing order of the calculated origin transition energies of monochlorophenols and phenol is in qualitative agreement with experimental results. Zero-point corrections are important in identifying the electronic spectra of monochlorophenols. The relative stabilities of rotational isomers, and dipole moments as well, have been also studied in relation to experimental results.

DOI： 10.1021/jp011533c

Language：English   Publishing type：Research paper (scientific journal)  

A new approach for elemental analysis, which is based on the measurement of the hard x ray emitted from a laser-produced plasma is reported here. Since the K-shell emission is characteristic of the element in a sample, Cu, Zn, Fe, Co, and Ni were readily confirmed to be present in brass and kovar alloys by measuring the x-ray emission spectrum over an energy range from 2 to 30 keV. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1405790

Language：English   Publishing type：Research paper (scientific journal)  

Capillary electrophoresis combined with semiconductor laser-induced fluorometry was applied to an immunoassay of human serum albumin. Human serum albumin was labeled with a fluorescent molecule (Cy5), which has an absorption maximum at 649 nm. The labeled albumin was purified by ultrafiltration in order to reduce signals, which are unreacted labeling reagent, product, and fragment products derived therefrom. After the purification, no signal for unreacted labeling reagent and fragment products was detectable in the electropherogram of the labeled albumin. The labeled albumin was then reacted with anti-albumin to form an immunocomplex, which was separated from the excess free albumin. The competitive immunoassay was used in the determination of human serum albumin in a controlled serum sample, using the labeled albumin. The obtained value was found to be 0.21±0.02 mg/ml, which is in good agreement with other known values. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0378-4347(01)00228-6

Language：English  

K-shell emission spectra of iron, copper, and molybdenum in the range of 1.5-20 keV using a 500 fs KrF excimer laser have been observed and are reported herein. © 2001 American Institute of Physics.

DOI： 10.1063/1.1342777

Language：Japanese   Publishing type：Research paper (scientific journal)  

Supersonic jet spectrometry (Review) - Fundamentals and applications to dioxin analysis
Imasaka T
BUNSEKI KAGAKU
50 (1): 3-30 JAN 2001

DOI： 10.2116/bunsekikagaku.50.3

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1143/JJAP.39.5115

Language：English  

The beam quality of a femtosecond dye/KrF excimer laser was improved using a pinhole, prepared from an acrylic plate. The pinhole acts as a volume light absorber that discriminates high-order transverse modes of the laser beam. A breakdown at the surface of the pinhole, which degrades the quality of the transmitted beam, can be avoided using this spatial filter. This approach was useful in minimizing self-phase modulation, which exhausts the limited laser energy and reduces the Raman output. A conversion efficiency of some vibrational and rotational emissions was improved, even though the laser pulse energy was substantially reduced by mode filtering.

DOI： 10.1143/JJAP.39.5115

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/S0039-9140(00)00423-9

Language：English   Publishing type：Research paper (scientific journal)  

Analysis of Thermal Decomposition Products Arising from Polyvinyl Chloride Analogs by Supersonic Jet/Multiphoton Ionization/Mass Spectrometry

Language：English  

An optical funnel, a new technique for the evaluation of the force of a microorganism, was applied to the determination of the motility force of bovine sperm cells. In this approach, sperm cells, suspended in an aqueous solution, are introduced into a now cell, to which radiation pressure is applied from the direction opposite to a medium flow. The sperm cell, which is moving in a stream, is captured by radiation pressure and forced to move to the position at which the force induced by the laser radiation is equal to the force induced by a medium now. The sperm cell then escapes by its own power on the way to this equilibrium (entrapping) position. The radiation force increases with decreasing distance from the focal point, and as a result, the force of the sperm cell can be determined by measuring the position where the sperm cell escaped against the laser irradiation field. The motility farce of the sperm cell was measured in aqueous solution at different pH values and potassium ion concentrations, It was possible to measure more than 250 sperm cells in 3 h, Thus, the optical funnel has potential for use as a rapid and repetitive means for the determination of the motility force of the sperm cell.

DOI： 10.1021/ac991458q

Language：English  

A new ionization scheme is proposed, in which the analyte molecule, ejected from a nozzle into a throat, is expanded from a repeller into a vacuum and immediately ionized and accelerated downstream for time-of-flight mass analysis. The ionization efficiency is improved by a factor of 50, which is in reasonably good agreement with the predicted value of 25, calculated from the distance between the nozzle and the ionization region for the cases of collinear (10 mm) and non-collinear (perpendicular) (50 mm) configurations. This approach has the unique capability for 'temperature tuning' of the analyte molecule by changing the position of the ionization region, thus permitting control of the spectral linewidth and, thereby, application of supersonic jet spectrometry to samples of unknown composition. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0003-2670(00)00757-1

Language：English  

The heat produced in conjunction with the processes of stimulated Raman scattering and four-wave Raman mixing in hydrogen was measured by photothermal refraction spectroscopy. Many vibrational, rotational, and vibrationally shifted rotational Raman lines are exclusively/simultaneously generated by changing the polarization of the laser beam and the hydrogen pressure. Thermal loss occurs predominantly from vibrational Raman scattering, which can be ascribed to a large Raman shift frequency of 4155 cm(-1) for the vibrational transition. In contrast to stimulated Raman scattering, Little or no thermal loss is observable during the process of four-wave Raman mixing.

DOI： 10.1007/s003400050057

Language：English   Publishing type：Research paper (scientific journal)  

Visualization of a Single Molecule Reaction in an Immunological Assay Based on Optical Chromatography

Language：English  

Optical chromatography, which is a technique for the separation of microscopic particles using a radiation force, is applied to kinetic studies of an immunoreaction. Polystyrene beads coated with antibodies react with antigens to produce conjugated beads, which comprise two beads and some antigens. The resulting conjugated beads are separated from the single beads. The detection limit of the antigen is <1 ng ml(-1), which is smaller than that reported in a previous paper [T. Hatano, T Kaneta, T. Imasaka, Anal. Chem. 69 (1997) 2711], and can be achieved using 2 mu m-diameter beads. The sensitivity in the present method can be further enhanced by increasing the particle size. In addition, the dissociation reaction of the conjugated beads is evaluated by using an on-column reaction technique, which allows the direct monitoring of the formation and dissociation of the conjugated beads. The rate constant for the dissociation of the conjugated beads is determined to be 4.0 x 10(-3) s(-1) for the case of conjugated beads combined by a single bond. (C)2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0003-2670(99)00669-8

Language：English  

DOI： 10.2116/analsci.15.1273

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ac990625j

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ac981315o

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.1149901

Language：English  

The intensities of high-order rotational Raman lines are calculated by computer simulation in the approximation of time-independent plane-wave pumping based on the currently accepted model used in studies of four-wave Raman mixing (FWRM). When the phases of the rotational lines are assumed to be slightly random, the intensities are drastically decreased. Such reduction in intensity becomes more serious with increasing phase distortion, indicating that the emission lines generated by FWRM requiring phase matching are coherently phased. In other words, phase matching is equivalent to phase locking or mode locking in FWRM. These results suggest that FWRM has potential for use in generating ultrashort optical pulses shorter than 1 fs. [S1050-2947(99)03206-0].

DOI： 10.1103/PhysRevA.59.4703

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ac000021b

Language：English   Publishing type：Research paper (scientific journal)  

Diffractive Optical Chemical Sensor Based on Light Absorption

Language：English  

Stimulated Raman scattering and four-wave Raman mixing are used for the generation of vacuum ultraviolet laser emission. A VUV spectrometer employing this vacuum ultraviolet source was designed and constructed for the evaluation of the phosphor materials currently used for a plasma display panel, which utilizes a Xe discharge and produces vacuum ultraviolet emissions at 147 nm and 173 nm to excite the inorganic phosphors. The emission spectrum and the temporal profile of the luminescence were measured by exciting the phosphor at various ultraviolet and vacuum ultraviolet wavelengths, in order to investigate the dynamic processes of the phosphor material. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0003-2670(99)00208-1

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/S0039-9140(98)00272-0

Language：English   Publishing type：Research paper (scientific journal)  

Stimulated Raman emission from liquid dibromomethane (vibrational Raman shift frequency, 588 cm(-1)) is introduced into hydrogen gas (rotational Raman shift frequency, 587 cm(-1)) as a seed beam, in order to generate numerous rotational lines by four-wave Raman mixing. Unexpectedly, a supercontinuum, which is generated by self-phase modulation in dibromomethane, acted as a seed beam to exclusively generate vibrational lines; the rotational lines are generated only when the supercontinuum is minimal. The former is explained by a competition between the high-gain vibrational and low-sain rotational Raman effects when strongly seeded by a supercontinuum. The latter is explained by stimulated Raman gain under the seed effect exclusively to the first-Stokes rotational line. (C) 1999 Elsevier Science B.V. All rights reserved.

Language：English   Publishing type：Research paper (other academic)  

Supersonic Jet Spectroscopy for Environmental Analysis

Language：English   Publishing type：Research paper (scientific journal)  

Indirect Detection of Amino-Substituted Polycyclic Aromatic Hydrocarbons in Cyclodextrin-Modified Micellar Electrokinetic Chromatography Combined with Diode Laser-Induced Fluorometry

Language：English   Publishing type：Research paper (scientific journal)  

The Generation of Powerful Rainbow-Color Laser Emission by Four-Wave Raman Mixing for Display and Illumination

Language：English  

DOI： 10.2116/analsci.14.1017

Language：English   Publishing type：Research paper (scientific journal)  

The “Optical Funnel”. A Technique for Measuring a Microorganism’s Power

Language：English  

Enantiomeric amino acids were labeled with a cyanine derivative (Cy5) for selective determination by capillary electrophoresis combined with diode laser-induced fluorometry. Cyanine-labeled glutamic acid has a high negative charge so that it was difficult to detect by conventional capillary zone electrophoresis due to its electrophoretic mobility being greater than the electroosmotic mobility. Thus, cyclodextrin-modified capillary gel electrophoresis using replaceable poly(vinylpyrrolidone) (PVP), which effectively suppresses the electroosmotic flow, was employed to separate Cy5-labeled amino acid enantiomers. The separation of six amino acid enantiomers could be achieved by using 1% PVP solution containing 70 mM gamma-cyclodextrin. It was also shown that PVP does not affect the selectivity of optical isomers. (C) 1998 Elsevier Science B.V.

DOI： 10.1016/S0021-9673(98)00023-5

Language：English  

Rotational Stokes emission is generated by focusing a linearly-polarized femtosecond pump beam into molecular hydrogen with a supercontinuum, which occurs by self phase modulation as a result of passing the beam through molecular nitrogen. The supercontinuum acts as a seed beam in the generation of rotational Stokes emission, However, enhancement of the supercontinuum by increasing the peak power suppresses the generation of the rotational Raman emission, due to a large gain fur the super-continuum and to the poor beam focusing capability of the pump beam, probably as a result of self focusing. (C) 1998 Elsevier Science B.V.

DOI： 10.1016/S0030-4018(97)00675-5

Language：English  

More than 40 rotational Raman lines are generated using an 800-fs Ti:sapphire laser. The spectral region extends from the near-infrared to the far-ultraviolet with a considerably flat intensity distribution. The effects of laser polarization, pulsewidth, hydrogen pressure, and focusing conditions on the efficiencies of stimulated Raman scattering, four-wave Raman mixing, self-phase modulation, self-focusing, and harmonic generation are investigated. A white light continuum, generated by self-phase modulation, acts as a seed beam for the generation of high-order rotational lines through four-wave Raman mixing, Strong self-phase modulation, however, suppresses the generation of the Raman emission, due to a line broadening of the pump beam. Thus, optimization of experimental conditions is necessary for the efficient generation of high-order rotational lines.

DOI： 10.1109/3.658704

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Halogenated benzenes and phenols are measured by multiphoton ionization mass spectrometry using femtosecond (150, 500 fs) and nanosecond (15 ns) laser pulses, The molecular ion is strongly enhanced for monohalobenzenes when the pulse width of the ionization laser is shorter than the lifetimes of their excited states. This is attributed to the reduction of intersystem crossing by a spin-orbit interaction, the so-called internal heavy-atom effect, and to rapid dissociation from the triplet state, A femtosecond laser pulse was deemed to be useful for the efficient ionization of dichlorobenzene and trichlorobenzene although their lifetimes are unknown, since polychlorinated benzenes are thought to have shorter lifetimes as the result of a stronger spin-orbit interaction, The ionization efficiencies of o-chlorophenol and p-chlorophenol are also obtained using femtosecond and nanosecond pulses, In the case of o-chlorophenol, intersystem crossing occurs more efficiently by stabilization of the triplet state by intramolecular hydrogen bonding, and as a result, the femtosecond pulse is more effective in ionizing o-chlorophenol, which has a shorter lifetime, These results indicate that an ultrashort laser pulse is very useful in improving the ionization efficiency for a molecule with a short lifetime, such as polychlorinated dioxins and their precursors.

DOI： 10.1021/ac9704624

Language：English   Publishing type：Research paper (scientific journal)  

Low-order transverse mode of dye laser emission was more efficiently converted into Stokes beams because of a high Raman gain coefficient, and the Stokes beams with near-TEM00 mode and good spectral purity were obtained from a multi-mode pump beam. High-order transverse mode remained and amplified spontaneous emission of the dye laser were removed by placing a pinhole at the beam waist, giving a flatter intensity distribution for the fundamental and Stokes emissions in the Raman spectrum.

DOI： 10.1143/jjap.36.L1440

Language：English  

Rotational Raman lines are generated by stimulated Raman scattering and four-wave Raman mixing using the fundamental (810 nm) and second harmonic emission (405 nm) of a Ti:sapphire laser. The intensity of the Raman emission. measured at the different wavelengths, were compared and confirmed to be more pronounced when a second harmonic emission is used as a pump beam. This is attributed to a larger Raman gain coefficient at shorter wavelengths and better beam quality obtained by the second harmonic generation, as predicted from theory.

DOI： 10.1143/JJAP.36.6376

Language：English  

The generation of more than 40 rotational stimulated Raman emission lines in hydrogen gas by use of a picosecond and femtosecond Ti:sapphire laser is reported. The spectral range of the emission lines extends from the near-infrared to the far-ultraviolet region. The resulting broad bandwidth allows the generation of a 0.6-fs pulse by coherent superposition, i.e., Fourier synthesis, of the emission lines.

Language：English  

Optical chromatography, a new separation technique involving the use of a radiation force and a medium flow, is used for trace analysis of protein. Two polystyrene beads, coated with antibody (anti-mouse IgG), are combined in the presence of an antigen (mouse IgG). The bound (B) and free (F) beads are readily separated by optical chromatography, and the B/F ratio can be correlated with the concentration of antigen (protein). Nanomolar concentrations of protein can be measured by this technique. The rates of the forward and reverse immunological reactions were independently determined by measuring the time of formation and dissociation, respectively, of the immunobeads.

DOI： 10.1021/ac970081q

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ac970079z

Language：English  

The chemical species produced as a result of the thermal decomposition of polystyrene are multiphoton ionized by 500 fs and 15 ns laser pulses. Femtosecond laser ionization gave a more structured mass spectrum and a higher ionization efficiency. This is likely due to the fact that ionization occurs faster than intramolecular relaxation, e.g. photodecomposition, under femtosecond laser pulses.

DOI： 10.1016/S0003-2670(96)00612-5

Language：English   Publishing type：Research paper (scientific journal)  

A portion of Nd:YAG laser emission is used as a pump beam for neat dibromomethane to generate vibrational stimulated Raman emission emitting at a Raman shift frequency of 588 cm(-1). This beam is aligned to be collinear with the other portion of the pump beam and is used as a seed beam for the generation of numerous rotational stimulated Raman emissions of hydrogen with a Raman shift frequency of 587 cm(-1). Because their Raman shift frequencies coincide, a multifrequency laser emission consisting of many rotational lines. in addition to vibrational lines, is generated by four-wave rotational Raman mixing.

DOI： 10.1143/jjap.36.L412

Language：English   Publishing type：Research paper (scientific journal)  

Detection of a Specific DNA Fragment by Free-Solution Capillary Electrophoresis Using a Fluorescent DNA Probe Measured by Semiconductor Laser-Induced Fluorometry

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/0039-9140(96)01978-9

Language：English  

A dye laser emitting at four different frequencies separated by 293.5 (=587/2) cm(-1) is made by inserting an etalon in the resonator cavity of the laser. This laser beam is focused into molecular hydrogen (rotational Raman shift frequency, 587 cm(-1)) to generate a multicolor laser beam consisting of more than 10 rotational lines in the vicinity of the fundamental lines by four-wave Raman mixing. Such rotational lines also occur in the vicinity of the vibrational Raman lines. Thus more than 25 emission lines appear simultaneously. This approach is useful to multiply the line density, i.e., the emission lines within a specified wavelength region.

DOI： 10.1007/BF02932065

Language：English  

More than thirty rotational lines equally spaced by 587 cm(-1) are generated simultaneously in the vicinity of the fundamental line by four-wave Raman mixing using a high-power picosecond Ti:Sapphire laser as a pump source and hydrogen as a Raman medium. Since the wavelength of this multifrequency laser emission extends from the near-infrared to the near-ultraviolet, it can be utilized as a tunable light source for picosecond spectroscopy. Because of the wide spectral bandwidth available, this procedure has great potential for the generation of ultrashort laser pulses by mode-locking these emission lines.

DOI： 10.1007/BF01095260

Language：English  

Photoablation products arising from polymer materials were examined by supersonic beam spectrometry, and the results are compared with those obtained by thermal decomposition, The high selectivity provided by supersonic beam spectrometry allows detection of minor species, e.g., styrene occurred from poly(alpha-methylstyrene) by cleavage of a methyl group and by proton rearrangement. Because ablation techniques involve high temperatures, thermally stable materials such as poly(p-methylstyrene) can be examined, The latter material is difficult to examine by thermal decomposition, even at 350 degrees C, It is also possible to differentiate between isomer ablation products, e.g., alpha-methylstyrene and p-methylstyrene, The instrumental setup described herein was used to examine several authentic samples, such as ABS resin (acrylonitrile-butadiene-styrene) and O-ring (SBR, styrene-butadiene rubber), as well as polystyrene foam, As a result, a styrene segment could be confirmed to be present in these materials, However, no evidence was found for its presence in a glue sample that was suspected to contain styrene on the basis of conventional mass spectrometry, The latter finding confirms the high degree of selectivity of the technique.

DOI： 10.1021/ac951045z

Language：English   Publishing type：Research paper (scientific journal)  

A femtosecond KrF excimer laser is focused into molecular hydrogen to generate a multifrequency laser beam, consisting of many vibrational and rotational lines, in a transient Raman regime. The intensity distribution is unchanged from 5 to 13 atm, in contrast to the case of nanosecond laser pump. The efficiency for generation of the rotational lines is improved by increasing the peak power, especially at longer wavelengths, indicating power-dependent and wavelength-dependent behavior of this Effect, as expected from theory. (C) 1995 Optical Society of America

DOI： 10.1364/OL.20.002072

Language：English  

Calixarene ethoxycarbonyl ester is synthesized and used as a host molecule in optical detection of 2-phenethylamine. A plasticized poly(vinyl chloride) membrane containing the calixarene and a fluorescent dye responds to 2-phenethylamine reversibly, and the sensitivity of an optode is increased by substitution of the ethoxycarbonyl ester for a hydroxy group in calixarene. However, a large interference response to pH is observed when the membrane contains calixarene. A phenolic proton is dissociated with an increase of pH, and fluorescence from the membrane is quenched by deprotonated calixarene, which causes the interference response to pH. The guest molecule of 2-phenethylamine is incorporated inside the calixarene, and the proton dissociation in calixarene occurs upon complexation. It results in the optode response to the guest molecule. The response to alkyl ammonium ions is also investigated, and the selectivity of the optide is discussed.

DOI： 10.1016/0925-4005(95)01674-0

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/0003-2670(95)00273-3

Language：English   Publishing type：Research paper (scientific journal)  

Prediction of Chemical Structure of Aromatic Hydrocarbons by Pattern Recognition of Spectral Lines Obtained by Fluorescence Spectrometry in a Supersonic Jet

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Optical Chromatography

Language：English   Publishing type：Research paper (scientific journal)  

Indirect Detection of Aromatic Hydrocarbons by Semiconductor Laser Fluorometry in Micellar Electrokinetic Chromatography

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/0003-2670(94)00450-Z

Language：English  

Polycyclic aromatic hydrocarbons (PAHs) were separated by micellar electrokinetic chromatography and were detected by laser fluorometry. The PAHs with large molecular weights were separated by using dimethylformamide as an organic modifier. A He-Cd laser (325 nm, 5 mW) or a blue semiconductor laser (415 nm, 50 μW) was used as an exciting light source. The detection limit ( S N = 3) for perylene was 1.4 × 10-7 M under He-Cd laser excitation or 3.4 × 10-7 M under semiconductor laser excitation. © 1995.

DOI： 10.1016/0003-2670(94)00317-F

Language：English   Publishing type：Research paper (scientific journal)  

Effect of Laser Linewidths on Efficiency in Generation of Equally-Spaced Multifrequency Beam by Four-Wave Rotational Raman Mixing

Language：English   Publishing type：Research paper (scientific journal)  

Effect of Organic Modifier on Resolution of Hydrophobic Compounds by Micellar Electrokinetic Chromatography

Language：English   Publishing type：Research paper (scientific journal)  

Development of High-Temperature Pulsed Slit Nozzle and Its Application to Supersonic Jet Absorption Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

Tunable Dye Laser with Variable Pulse Width for Investigation of Nonlinear Optical Effect

Language：English   Publishing type：Research paper (scientific journal)  

Capillary Micellar Electrokinetic Chromatography Based on Indirect Semiconductor Laser Fluorescence Detection

Language：English   Publishing type：Research paper (scientific journal)  

Generation of Multi-Frequency Laser Emission and Its Application to Excitation Source in Supersonic Jet Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

Photoacoustic Spectrometry Using Fiber-Optic Pressure Sensor

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

A urea optrode was constructed using a polymer membrane optically sensitive to ammonium ions and a urease-immobilized membrane. A plasticized poly(vinyl chloride (PVC) membrane containing polynactin was prepared on the distal end of an optical fibre. The PVC membrane was covered with a polyacrylamide membrane, and a positively charged fluorescent dye of hexadecyl-acridine orange was immobilized on the PVC membrane through the polyacrylamide membrane to form an ammonium ion-sensitive membrane. The composite membrane was covered with another polyacrylamide membrane in which urease was immobilized. Urea in a sample solution was hydrolysed to ammonium ion by the immobilized urease and detected optically by the ammonium ion-sensitive membrane. The response of the optrode was reversible to urea concentration in the range 10(-4)-0.1 M, the response time being 40 s. The selectivity coefficients for potassium and sodium ions were 0.3 and 5 x 10(-4), respectively. The optrode was applied to the determination of urea in blood serum. The observed concentration was corrected for the interference of potassium ion, and it agreed well with the specified urea concentration. The diameter of the optical fibre was 140 mum, so that the optrode could be easily applied to in vivo measurements.

Language：English   Publishing type：Research paper (scientific journal)  

Subattomole Detection of Amino Acids by Capillary Electrophoresis Based on Semiconductor Laser Fluorescence Detection

Language：English   Publishing type：Research paper (scientific journal)  

High-Temperature Pulsed Slit Nozzle for Supersonic Jet Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

A supersonic jet spectrum of 9,10-dichloroanthracene is measured by stimulated-emission-pumping fluorescence dip spectrometry and conventional fluorescence spectrometry. The performance obtained is compared for these spectrometric methods, providing same information concerned with the energy level of the ground state. The former is more preferential for measurement of a high-resolution spectrum, since the spectral resolution is determined by the linewidth of the dumping laser. On the other hand, the latter is more preferential for measurement with better sensitivity at the expense of the spectral resolution, since the fluorescence throughput can be improved by increasing the slit width of the monochromator.

Language：English  

A laser beam at two different frequencies separated by 587 cm-1 is focused into pressurized hydrogen (rotational transition energy, 587 cm-1) to generate multi-color stimulated Raman emission. The polarization state and the pulse energy are measured for each generated emission line using linearly and circularly polarized pump beams. The effect of the polarization is discussed by using a parameter characterizing the polarizability of hydrogen and a conservation rule for the angular momentum in four-wave mixing. Many rotational lines are generated with linearly polarized pump beams through a four-wave mixing process. This is in striking contrast to the results obtained by using a single-color circularly polarized pump beam which generates only one rotational line through a conventional stimulated Raman process.

Language：English   Publishing type：Research paper (scientific journal)  

An optrode selective to potassium ions is constructed using a poly(vinyl chloride) (PVC) membrane and a positively charged fluorescent dye sensitive to polarity. Potassium ions in an aqueous solution are selectively extracted into the membrane, and the dye moves toward the aqueous solution by ion exchange with potassium ions. This concerted reaction causes an increase of polarity around the dye, resulting in the optrode response. A theoretical response curve, which agrees fairly well with the experimental result, is calculated based on the proposed mechanism. The optrode does not respond directly to a cationic surfactant, but the sensitivity of the optrode to potassium ions decreases with an increase of the concentration of the cationic surfactant. Thus the cationic surfactant can be measured by the potassium-ion optrode. This interference response is ascribed to a decrease in the extraction rate constant of potassium ions. The interference response is calculated based on this mechanism, and agrees well with the experimental result. The response of the optrode to anionic and non-ionic surfactants is investigated in detail, and a similar interference response is found for a non-ionic surfactant.

DOI： 10.1016/0925-4005(93)85273-D

Language：English  

Polystyrene and polyalpha-methylstyrene are thermally decomposed, and the products are measured by fluorescence spectrometry and multiphoton ionization spectrometry. The monomers are found to be major products from both the polymers, but many other chemical species, including dimers and trimers, are also observed. The present instrument is applied to a mixture sample containing these two polymers, and the components included are selectively determined using this hyphenated technique.

DOI： 10.1016/0039-9140(93)80331-K

Language：English   Publishing type：Research paper (scientific journal)  

A New Approach for the Generation of Ultrashort Optical Pulses

Language：English   Publishing type：Research paper (scientific journal)  

Supersonic Jet Spectrometry of Chemical Species Resulting from Thermal Decomposition of Polystyrene and Polycarbonate

Language：English   Publishing type：Research paper (scientific journal)  

Generation of Multifrequency Laser Emission by Injection of Two-Color Beam into Dye/Raman Composite Resonator

Language：English   Publishing type：Research paper (scientific journal)  

Determination of Amino Acids by Capillary Zone Electrophoresis Based on Semiconductor Laser Fluorescence Detection

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/0003-2670(92)85318-Z

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/an9911601407

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Fluorometric Determination of Potassium Ion Using Hexadecyl-Acridine Orange Immobilized on a Poly(vinyl chloride) Membrane Attached to a Flow-Through Cell

Language：English   Publishing type：Research paper (scientific journal)  

Methylene blue is converted to colourless leucomethylene blue in the presence of diaphorase and reduced nicotinamide adenine dinucleotide (NADH). Thus an enzyme reaction producing NADH can be monitored by visible semiconductor laser spectrometry of methylene blue, which has an absorption band in the red region at 670 nm. Lactate dehydrogenase (LDH) is determined by absorption spectrometry using a batch cell. A human serum sample containing 0.2 U ml-1 of LDH is easily detected in a reaction period of 5 min. A flow system is used to remove the effect of oxidation of leucomethylene blue by oxygen dissolved in the sample solution for quantitative analysis. Alcohol dehydrogenase is determined by fluorimetry down to 4 mU, the detection limit of ethanol being 10 nmol.

Language：English   Publishing type：Research paper (scientific journal)  

When a sample molecule is excited to high vibrational levels in the excited state, rapid intramolecular relaxation occurs by an interaction with a dense manifold of vibrational levels in the ground state. Due to vibronic mixing, a combination of vibrational quanta is redistributed and the state is no longer identical with the initial state excited. Therefore, a complicated and broad-band structure appears in a conventional excitation spectrum, due to breakdown of selection rules. This common feature in supersonic jet spectrometry makes it difficult to assign a specific component even for a sample containing only a single interference compound. For example, selective detection of beta-naphthol is difficult for a sample containing anthracene, and this situation is similar to m-toluidine and 2-methylnaphthalene. However, this unwanted photoemission is completely suppressed by a combination of supersonic jet spectrometry and synchronous scan luminescence spectrometry monitoring resonance fluorescence (SSJ/R-SSL). Furthermore, the number of spectral lines is reduced, giving a simpler spectrum. Thus SSJ/R-SSL spectrometry provides a useful analytical means for selective analysis of organic molecules such as polycyclic aromatic hydrocarbons.

Language：English   Publishing type：Research paper (scientific journal)  

The ratio of the signal intensities obtained in multiphoton ionization spectrometry and fluorescence spectrometry are compared semi-quantitatively for several aromatic hydrocarbons. The ratios, normalized against N-ethylaniline, are 0.2-1 for aniline derivatives, however, the value for antrace is 7 x 10(-6) in a one-colour ionization scheme and 7 x 10(-4) in a two-colour ionization scheme. The small value obtained for the 'large' aromatic hydrocarbon is ascribed to the high ionization potential relative to the two-photon energy for excitation and succeeding ionization; three photons are required in the one-colour scheme and an additional laser with sufficient energy must be aligned temporally and spatially for ionization in the two-colour scheme.

Language：English   Publishing type：Research paper (scientific journal)  

Two-Color Stimulated Raman Effect of Para-Hydrogen

Language：English   Publishing type：Research paper (scientific journal)  

Synchronous Scan Luminescence Techniques Monitoring Resonance and Nonresonance Fluorescence in Supersonic Jet Spectrometry Applied to Anthracene Derivatives

Language：English   Publishing type：Research paper (scientific journal)  

Determination of Proteins by Gel Electrophoresis Combined with Visible Semiconductor Laser Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

Thermal Lens Spectrophotometry of Nitrogen Dioxide Using an Excimer-Laser-Pumped Dye Laser

Language：English   Publishing type：Research paper (scientific journal)  

Efficiently Generated Rotational and Vibrational Stimulated Raman Emission by Means of a Two-Color Laser Beam

Language：English   Publishing type：Research paper (scientific journal)  

The cobalt(II) complex is detected spectrophotometrically by its catalysis of a photochromic isomerism of norbornadiene (NBD). NBD is immobilized on porous glass beads, and is isomerized to quadricyclane (QC) by UV irradiation. The beads are then immersed in a solution containing tetraphenylporphinecobalt(II) [TPPCo(II)], and the QC is converted back to NBD by a catalytic reaction with TPPCo(II). The rate constant, measured spectrophotometrically, is proportional to the concentration of TPPCo(II). The detection limit of TPPCo(II) is 60-mu-M for a reaction period of 1 h. This spectrophotometric detection can be applied repetitively without any supply of the chemical reagent, as NBD immobilized on the porous glass beads can be re-isomerized to QC by UV irradiation.

Language：English   Publishing type：Research paper (scientific journal)  

A two-color laser beam separated by 587 cm-1 is focused into pressurized hydrogen to generate stimulated Raman emission. By optimizing the hydrogen pressure and the beam focusing condition, only rotational lines are generated in the near-UV region; the vibrational lines are completely suppressed. The rotational lines are further enhanced by using a circularly polarized beam.

Language：English   Publishing type：Research paper (scientific journal)  

The concentration of Fe(II) ion is determined by chelation with 2-nitroso-5-diehtylaminophenol and liquid-liquid extraction into chloroform. Light absorption at 780 nm is measured with a thermal lens spectrophotometer equipped with a semiconductor laser as a light source. The enhancement factor achieved experimentally is 47. The detection limit of Fe(II) ion is 8.1 x 10(-9) M, which is 3-4 time better than that obtained by conventional absorption spectrometry, and is governed by the background signal originating from Fe(II) impurity in the reagent.

Language：English   Publishing type：Research paper (scientific journal)  

Enzyme Immunoassay of Insulin by Semiconductor Laser Fluorometry

Language：English   Publishing type：Research paper (scientific journal)  

Development of a Widely-Tunable, Multi-Color Laser and Its Application to Analytical Spectroscopy

Language：English   Publishing type：Research paper (scientific journal)  

Determination of Surfactant by Visible Semiconductor Laser Fluorometry after Solvent Extraction with Rhodamine 800

Language：English   Publishing type：Research paper (scientific journal)  

Ion-Selective Optrode Using Hexadecyl-Acridine Orange Attached on Poly(vinyl chloride) Membrane

Language：English   Publishing type：Research paper (scientific journal)  

Fiber-Optic Potassium Ion Sensor Using Alkyl-Acridine Orange in Plasticized Poly(vinyl chloride) Membrane

Language：English   Publishing type：Research paper (scientific journal)  

Analytical Instrumentation Based on Optical Harmonic Generation

Language：English   Publishing type：Research paper (scientific journal)  

A two-color laser beam separated by 587 cm- is focused into a Raman cell pressurized with hydrogen. More than fifty rotational and vibrational lines are generated by a four-wave mixing-assisted stimulated Raman effect. By synchronously changing the laser frequencies, the overall tuning range is extended from the deep ultraviolet (247 nm) to the near infrared (771 nm) without any frequency gaps. © 1990 Optical Society of America.

DOI： 10.1364/AO.29.001727

Language：English   Publishing type：Research paper (scientific journal)  

Thin-Layer Chromatography with Supersonic Jet Fluorometric Detection

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Visible Fluorescence Spectrometry Using Second Harmonic Emission Self-Induced in Semiconductor Laser as a Light Source

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Laser Ablation/Supersonic Jet/Fluorescence Spectrometry of Large Aromatic Hydrocarbon

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Fiber-Optic Calcium(II) Sensor with Reversible Response

Language：English   Publishing type：Research paper (scientific journal)  

Supersonic Jet/Synchronous Scan Luminescence Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

Optical-Fiber Sensor Based on the Second-Harmonic Emission of a Near-Infrared Semiconductor Laser as Light Source

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Semiconductor Laser Fluorimetry for Enzyme and Enzymatic Assays

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Evaluation of Chemical Structure from Sharp Line Structure in Supersonic Jet Spectrum

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Thermal Lens Spectrophotometry Using a Tunable Infrared Laser Generated by a Stimulated Raman Effect

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Capillary Gas Chromatograph Determination of Aniline Derivatives by Supersonic Jet Resonance Multiphoton Ionization Mass Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

High-Performance Liquid Chromatographic Detector Based on Near-Infrared Semiconductor Laser Fluorimetry

Language：English   Publishing type：Research paper (scientific journal)  

Ultramicro Flow-Cell for Semiconductor Laser Fluorimetry

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Laser Fluorimetry of Polynuclear Aromatic Hydrocarbons Based on Time-Resolved Fluorescence Detection

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Pulsed Semiconductor Laser Fluorometry for Lifetime Measurements

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Thermal Lens Spectrophotometry with Argon Laser Excitation Source for Nitrogen Dioxide Determination

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Ultratrace Photometric Determination of Phosphate with a Solid-State Emitter as Light Source

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Semiconductor Lasers and Solid-State Emitters as Near-Infrared Light Sources for Photoacoustic Spectroscopy

Language：English   Publishing type：Research paper (scientific journal)  

Determination of Nitrogen Dioxide by Pulsed Thermal Lens Spectrophotometry

Language：Japanese   Publishing type：Research paper (scientific journal)  

Trace Analysis of Benzene by Thermal Lens Spectrometry Using a Carbon Dioxide Laser

Language：English   Publishing type：Research paper (scientific journal)  

Thermal Lens Spectrophotometry Based on Pulsed Laser Excitation

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Thermal Lens Spectrophotometry Based on Image Detection of a Probe Laser Beam

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Application of Microcomputer for Data Processing in Flow Injection Analylsis

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Laser Fluorimetric Systems for Ultra-Trace Analysis

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

ULTRA-SENSITIVE DETERMINATION OF PYRENE ON THE BASIS OF TIME-RESOLVED LASER FLUOROMETRY

Language：English   Publishing type：Research paper (scientific journal)  

High Repetition Rate Atmospheric Pressure Nitrogen Laser for Lifetime Measurements

Language：English   Publishing type：Research paper (scientific journal)  

Application of the Thermal Lens Effect for Determination of Iron(II) with 4,7-Diphenyl-1,10-Phenanthroline Disulfonic Acid

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Enzyme Amplification Laser Fluorimetry

Language：Japanese   Publishing type：Research paper (scientific journal)  

Detectiion of Nitrogen Dioxide by Laser Fluorescence Spectrometry

Language：English   Publishing type：Research paper (scientific journal)  

Laser Fluorometry of Fluorescein and Riboflavin

Language：English   Publishing type：Research paper (scientific journal)  

Laser Fluorescence Immunoassay of Insulin

Language：English   Publishing type：Research paper (scientific journal)  

Nanosecond Time-Resolved Spectrometry with a Tunable Dye Laser and a Simple Pulse-Gated Photon Counter

Language：English   Publishing type：Research paper (scientific journal)  

Time-Resolved Spectroscopy on the Excited Electronic States of NO2 in the Neighborhood of 454.6 nm

Language：English   Publishing type：Research paper (scientific journal)  

Detection Limit of Fluorescein as Determined by Fluorometry with an Esculin Laser Source

Language：English   Publishing type：Research paper (scientific journal)  

Time-Resolved Fluorescence Spectra of Nitrogen Dioxide Excited at 450.4 nm by a 4-Methylumbelliferone Laser

Language：Japanese   Publishing type：Research paper (scientific journal)  

Development of Fluorescence Spectrometer Using an Organic Solution Laser Source and Its Application to a Few Gaseous Molecules

Language：English   Publishing type：Research paper (scientific journal)  

Characteristics of Coordination Compounds of Calcein Blue for a Tunable Organic Liquid Laser

Language：English   Publishing type：Research paper (scientific journal)  

Formation of Diacetylene Ion (A²IIu) by Controlled Electron Impact on Unsaturated Molecules

Language：English   Publishing type：Research paper (scientific journal)  

Emission Spectra of Dimethoxybenzenes by Controlled Electron Impact

Language：English   Publishing type：Research paper (scientific journal)  

Coordination Compounds of Calcein Blue for New Laser Material

Responsible for pages：14.3-4, 1390-1410   Language：Japanese   Book type：Scholarly book

"Hyphenated Liquid Chromatograph System and Other Methods" Analytical Chemistry -The Approved Text to the FECS Curriculum: Analytical Chemistry-, Ed. R A. Kellner, J. M. Mermet, M. Otto, H. M. Widmer, WILEY-VCH Verlag GmbH, Weinheim, Germany, 1998.

Responsible for pages：5, 2780-2788   Language：English   Book type：General book, introductory book for general audience

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