Akihiro Arai - Academia.edu (original) (raw)

Papers by Akihiro Arai

IEEJ Transactions on Sensors and Micromachines, 2001

Journal of Chromatography A, 1992

The effect of pH on the electrophoretic migration properties of single-stranded oligodeoxyribonuc... more The effect of pH on the electrophoretic migration properties of single-stranded oligodeoxyribonucleotides in capillary gel electrophoresis was investigated. Different homooligodeoxyribonucleotides of equal chain length showed significant differences in relative migration when the pH of the gel buffer was varied from pH 6 to 8, parallel with the running buffer. A similar variation in migration order was observed during the electrophoretic equilibration of a pH 8 gel-filled capillary column with a pH 6 running buffer. In the latter instance, the current reached the new level after 20 min of electrophoretic equilibration with the pH 6 running buffer. However, it was observed that the migration order characteristic of the pH 6 gel was achieved only after 4 h of electrophoretic equilibration. To avoid this time-consuming equilibration process, these results suggest that gel-filled capillary columns should be prepared with the same buffer (composition and pH) that will be used as the running buffer during the separations.

Journal of Chromatography A, 2000

Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quar... more Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quartz microchips have two main channels and four reservoirs. Dansyl-lysine and-glycine were separated and detected with bis[(2-(3,6,9-trioxadecanyloxycarbony)-4-nitrophenyl]oxalate as peroxyoxalate chemiluminescent reagent. These dansyl amino acids came into contact with the chemiluminescence reagent to produce visible light at the interface between the separation channel and 25 chemiluminescence reagent-containing reservoir. The detection limit (S /N53) for dansyl-lysine was 1?10 M, which corresponded to the very small mass detection limit of ca. 0.4 fmol. However, the concentration sensitivity in the present system was approximately two orders of magnitude lower than that in the conventional capillary electrophoresischemiluminescence detection system. The relative standard deviations of migration time and peak height for dansyl-lysine were 4.2 and 4.5%, respectively. A channel conditioning before every run and an appropriate control of voltages were needed for the reproducible results. The present system had advantages in rapid separation time (within 40 s), small (several 10 pl) and accurate sample injection method using a cross-shaped injector, and simplification and miniaturization of the detection device.

Journal of Chromatography A, 2004

Analyses of amino acids and peptides were performed using a quartz microchip and an interface for... more Analyses of amino acids and peptides were performed using a quartz microchip and an interface for microchip electrophoresis-electrospray ionization mass spectrometry (MCE-ESI-MS). In MCE-ESI-MS, negative pressure caused by ESI increased band broadening and deteriorated separation. We tried to suppress the negative pressure and improve separation using a microchip with a long separation channel. Separations of peptide standards were compared using two microchips with long separation channel (58.9 mm) and short one (22.9 mm). Theoretical plate numbers and resolution were improved significantly using the former. The theoretical plate numbers of [Val4]angiotensin was 8600 using the former and 1700 using the latter. When background electrolytes of low pH were used in an uncoated quartz microchip, electrokinetic injection was difficult because of weak electroosmotic flow. The use of successive multiple ionic polymer layers coating of the microchip channel stabilized electrokinetic injection and permitted analysis of amino acids and peptides even under low pH conditions. Separation of amino acids was successfully performed using formic acid solution (pH 2.5) as background electrolyte.

ELECTROPHORESIS, 2004

Performance of electrokinetic supercharging for high-sensitivity detection of DNA fragments in ch... more Performance of electrokinetic supercharging for high-sensitivity detection of DNA fragments in chip gel electrophoresis Chip gel electrophoresis was explored for high-sensitivity detection of DNA by combining electrokinetic injection with transient isotachophoresis preconcentration (here named electrokinetic supercharging (EKS)). Low concentrations (0.2 mg/L) of DNA sample could be detected without fluorescence labeling using a conventional UV detector (at 260 nm). On a single-channel microchip, identification of PCR product was performed by exploiting both external and internal calibration methods. The deviation between the two calibration methods was about 3.6%, and the identified DNA fragment size matched with the predicted size of the template DNA. On the cross microchip the EKS preconcentration has also been achieved when changing the injection reservoir differing from the one used previously. The procedure was computer-simulated and the influence of the voltage applied to two-side reservoirs on sample preconcentration and dilution was also discussed.

Chemistry Letters, 2012

ABSTRACT An open-tubular capillary chromatography system has been developed using a ternary mixed... more ABSTRACT An open-tubular capillary chromatography system has been developed using a ternary mixed solvent solution, i.e., water-hydrophilic/hydrophobic organic solvent mixture as a carrier solution. The system is called "tube radial distribution chromatography (TRDC)." In this study, we tried to carry out the TRDC on a microchip incorporating microchannels. A model analyte solution of isoluminol isothiocyanate (ILITC) and ILITC-labeled bovine serum albumin (BSA) was injected to the double T-junction part (0.5 mm length, ca. 2 nL) on the microchip. The analyte solution was then delivered in the separation microchannel (40 mu m in depth, 100 mu m in width, and 22 cm in length) with a ternary water-acetonitrile-ethyl acetate mixture carrier solution (3:8:4, volume ratio). The model analytes, the ILITC and the labeled BSA were separated through the microchannel, where the carrier solvents were radially distributed in the separation channel generating inner and outer phases. This phenomenon of the solvents is called "tube radial distribution phenomenon (TRDP)." The outer phase functions as a pseudo-stationary phase under laminar flow conditions in the chromatography, i.e., TRDC. Finally, the ILITC and the labeled BSA were eluted in this order and detected with chemiluminescence reaction.

Bulletin of the Chemical Society of Japan, 1989

A highly sensitive fiber-optic immunosensor using an antibody-immobilized optical fiber was devel... more A highly sensitive fiber-optic immunosensor using an antibody-immobilized optical fiber was developed and introduced into a chemiluminescence complex catalyst immunoassay (CLCCIA) which had been reported by the authors in a previous paper. After optimization of the experimental conditions, human serum albumin as model protein was determined by both competitive immunoassay and sandwich immunoassay, using the fiber-optic immunosensor. Human serum albumin could be determined in the concentration range 1×10−4–1×10−1 g dm−3 with a lower limit of 400 pg by competitive immunoassay while in the concentration range 1×10−5–1×10−1 g dm−3 with a lower limit of 40 pg by sandwich immunoassay. The new fiber-optic immunosensor developed by the authors can be characterized as follows: 1) Highly sensitive for the determination of a small amount of protein, 2) applicable to a wide concentration range of protein sample, 3) feasible with a microvolume of sample, 4) suitable for automated operation, and 5) excellent regarding ...

Analytical Sciences, 2000

SEIBUTSU BUTSURI KAGAKU, 2008

Nucleic Acids Symposium Series

The LIGA (Lithographie Galvanoformung Abformung) process using synchrotron radiation lithography ... more The LIGA (Lithographie Galvanoformung Abformung) process using synchrotron radiation lithography is applied to the microfabrication of capillary array electrophoresis (CAE) device. Laser-induced fluorescence detection system for the CAE device has been constructed by the modification of laser confocal fluorescence microscopy. DNA molecules were detected during migrating in the microchannels filled with polymer separation matrices under electric field to optimize the separation conditions for DNA analysis. Based on this observation, we demonstrated that microfabricated CAE device is realized the fast separation of DNA.

SEIBUTSU BUTSURI KAGAKU, 2008

This paper describes the concept of MCE-202 "MultiNA", a new microchip electrophoresis system for... more This paper describes the concept of MCE-202 "MultiNA", a new microchip electrophoresis system for DNA/RNA analysis. MCE-202 "MultiNA" realizes high-throughput and cost-effective analysis with originally developed reusable microchips and reagent kits. Application data for Norovirus detection and meat identification are also presented.

Rapid Communications in Mass Spectrometry, 2006

A system of microchip capillary electrophoresis/electrospray ionization mass spectrometry (mchip-... more A system of microchip capillary electrophoresis/electrospray ionization mass spectrometry (mchip-CE/ESI-MS) for rapid characterization of proteins has been developed. Capillary electrophoresis (CE) enables rapid analysis of a sample present in very small quantity, such as at femtomole levels, at high resolution. Faster CE/MS analysis is expected by downsizing the normal capillary to the microchip (mchip) capillary. Although rapidity and high resolution are advantages of CE separation, electroosmotic flow (EOF) instability caused by the interaction between proteins and the microchannel surface results in low reproducibility in the analysis of basic proteins under neutral pH conditions. By coating the microchannel surface with a basic polymer, polyE-323, basic proteins, which have pI values of over 7.5, could be separated and detected by mchip-CE/MS on quadrupole (Q) and time-offlight (TOF) hybrid instruments. By increasing the cone and collision voltages during the analysis by mchip-CE/ESI-MS of a small protein, some product ions, which contain the sequence information, could also be obtained, i.e., 'top-down' analysis of the protein could be accomplished with this mchip-CE/MS system. To our knowledge, this is the first report of 'top-down' analysis of a protein by mchip-CE/MS. Since it requires a much shorter time and a smaller sample amount for analysis than the conventional liquid chromatography (LC)/ESI-MS method, mchip-CE/MS promises to be suitable for the high-throughput characterization of proteins.

Journal of Chromatography A, 2004

We demonstrate a convenient single-step quantitation technique for double-stranded DNA (dsDNA) fr... more We demonstrate a convenient single-step quantitation technique for double-stranded DNA (dsDNA) fragments in polymerase chain reaction (PCR) products based on microchip capillary electrophoresis (micro-CE)/UV or fluorescence detection. PCR products of polymorphisms on the human Y-chromosome related to spermatogenic failure did not need purification. They were premixed and comigrated with a DNA digest whose concentration was known. Hydroxyethyl cellulose (HEC) dissolved in 5x Tris-borate-EDTA (5x TBE, pH 8.3) was used as a separation matrix in a linear polyacrylamide-coated quartz microchip, while mixed poly(ethyl oxides) (PEOs) of different molar-masses dissolved in 1 x TBE (pH 8.3) containing 1 ng/microl ethidium bromide was used as a separation matrix in an uncoated poly(methyl methacrylate) (PMMA) microchip. Elution profiles were monitored under either real-time linear imaging UV detection in the snapshot mode where the total separation time is fixed, or light-emitting diode (LED) confocal fluorescence detection in the finishline mode where solutes migrate over the same separation length. It is found that, in both modes, a linear relation exists between the peak areas (A) and the multiplication of the digest concentrations (C) and the fragment sizes (L) in a DNA restrictive digest. Using the comigration electropherogram of a single-step experiment, the concentrations of PCR products were directly determined using the A versus LC linear relationship. The sole condition to obey is that the chosen digest has different fragment sizes with the PCR products of interest. This condition is easy to obey, because micro-CE owns high separation ability, and many digests are commercially available. The recovery of the technique was between 98 and 105%. The R.S.D. for chip-to-chip concentration measurements was less than 6.0% (n = 6). Hence, the technique was accurate and reliable for DNA assays.

Journal of Chromatography A, 2003

A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was develo... more A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was developed using a spray nozzle connected to the exit of the separation channel of the microchip. The spray nozzle was attached to the microchip using a polyether ether ketone screw without adhesive, thus allowing easy replaced. Sample injection and electrophoretic separation was performed by control of the voltage only. The analysis of a few basic drugs was performed using the optimized MCE-MS system. The separation was improved by using a high-viscosity separation buffer and a spray nozzle with a small bore size. This system was also applied to the separation of peptides and protein-trypsin digests. Sample adsorption was minimized by adding acetonitrile to the separation buffer when using a quartz microchip.

ELECTROPHORESIS, 2001

We have proposed a field-inversion electrophoresis on a microchip for a shorter effective length,... more We have proposed a field-inversion electrophoresis on a microchip for a shorter effective length, and investigated the external frequency for the DNA analysis based on the field-inversion electrophoresis device. By using the optimized frequency, we demonstrated that the field-inversion electrophoresis has great potentials for the separation of DNA fragments with shorter effective length.

ELECTROPHORESIS, 2003

High-speed electrophoretic analysis of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosacchari... more High-speed electrophoretic analysis of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosaccharides on a quartz microchip with whole-channel UV detection 1-Phenyl-3-methyl-5-pyrazolone (PMP) derivatives of monosaccharides were analyzed by electrophoresis on a quartz microchip with whole-channel UV detection. Rapid separation of PMP derivatives of aldopentoses was achieved by plain-zone electrophoresis in a neutral phosphate buffer with the height equivalent to a theoretical plate at the micrometer level. Zone electrophoresis as borate complexes was also successful for the separation of PMP derivatives of a few aldoses, which were separated within 1 min. Separation by microchip electrophoresis was compared to that by capillary electrophoresis, and the difference was discussed in terms of column efficiency and sample column capacity.

ELECTROPHORESIS, 2001

Microchip electrophoresis for the short-time analysis of amino sugars is described. D-Glucosamine... more Microchip electrophoresis for the short-time analysis of amino sugars is described. D-Glucosamine, D-galactosamine and their reduced forms were labeled with 4-nitro-2,1,3-benzoxadiazole 7-fluoride (NBD-F) at pH 6.0 and the fluorescent derivatives were purified on an octadecyl silica (ODS) gel plate. The derivatives were analyzed by electrophoresis on a microfabricated chip with a 33 mm long separation channel with argon laser-induced fluorescence detection. Under the established conditions, these amino sugarderivatives were well separated from each other within 60 s. Amino sugars of as small an amount as 0.5 fmol could be detected with a signal-to-noise (S/N) ratio of 3, and peak response showed good linearity between at least 0.8 and 8 fmol of samples with a relative standard deviation (RSD) of ca. 4%. This method was also applied to the analysis of amino sugar composition of O-linked glycans released from bovine submaxillary mucin with alkali in the presence of borohydride. The result of amino sugar composition analysis for individual O-glycans fractionated by high-performance liquid chromatography was quite useful for their identification.

IEEJ Transactions on Sensors and Micromachines, 2001

Journal of Chromatography A, 1992

The effect of pH on the electrophoretic migration properties of single-stranded oligodeoxyribonuc... more The effect of pH on the electrophoretic migration properties of single-stranded oligodeoxyribonucleotides in capillary gel electrophoresis was investigated. Different homooligodeoxyribonucleotides of equal chain length showed significant differences in relative migration when the pH of the gel buffer was varied from pH 6 to 8, parallel with the running buffer. A similar variation in migration order was observed during the electrophoretic equilibration of a pH 8 gel-filled capillary column with a pH 6 running buffer. In the latter instance, the current reached the new level after 20 min of electrophoretic equilibration with the pH 6 running buffer. However, it was observed that the migration order characteristic of the pH 6 gel was achieved only after 4 h of electrophoretic equilibration. To avoid this time-consuming equilibration process, these results suggest that gel-filled capillary columns should be prepared with the same buffer (composition and pH) that will be used as the running buffer during the separations.

Journal of Chromatography A, 2000

Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quar... more Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quartz microchips have two main channels and four reservoirs. Dansyl-lysine and-glycine were separated and detected with bis[(2-(3,6,9-trioxadecanyloxycarbony)-4-nitrophenyl]oxalate as peroxyoxalate chemiluminescent reagent. These dansyl amino acids came into contact with the chemiluminescence reagent to produce visible light at the interface between the separation channel and 25 chemiluminescence reagent-containing reservoir. The detection limit (S /N53) for dansyl-lysine was 1?10 M, which corresponded to the very small mass detection limit of ca. 0.4 fmol. However, the concentration sensitivity in the present system was approximately two orders of magnitude lower than that in the conventional capillary electrophoresischemiluminescence detection system. The relative standard deviations of migration time and peak height for dansyl-lysine were 4.2 and 4.5%, respectively. A channel conditioning before every run and an appropriate control of voltages were needed for the reproducible results. The present system had advantages in rapid separation time (within 40 s), small (several 10 pl) and accurate sample injection method using a cross-shaped injector, and simplification and miniaturization of the detection device.

Journal of Chromatography A, 2004

Analyses of amino acids and peptides were performed using a quartz microchip and an interface for... more Analyses of amino acids and peptides were performed using a quartz microchip and an interface for microchip electrophoresis-electrospray ionization mass spectrometry (MCE-ESI-MS). In MCE-ESI-MS, negative pressure caused by ESI increased band broadening and deteriorated separation. We tried to suppress the negative pressure and improve separation using a microchip with a long separation channel. Separations of peptide standards were compared using two microchips with long separation channel (58.9 mm) and short one (22.9 mm). Theoretical plate numbers and resolution were improved significantly using the former. The theoretical plate numbers of [Val4]angiotensin was 8600 using the former and 1700 using the latter. When background electrolytes of low pH were used in an uncoated quartz microchip, electrokinetic injection was difficult because of weak electroosmotic flow. The use of successive multiple ionic polymer layers coating of the microchip channel stabilized electrokinetic injection and permitted analysis of amino acids and peptides even under low pH conditions. Separation of amino acids was successfully performed using formic acid solution (pH 2.5) as background electrolyte.

ELECTROPHORESIS, 2004

Performance of electrokinetic supercharging for high-sensitivity detection of DNA fragments in ch... more Performance of electrokinetic supercharging for high-sensitivity detection of DNA fragments in chip gel electrophoresis Chip gel electrophoresis was explored for high-sensitivity detection of DNA by combining electrokinetic injection with transient isotachophoresis preconcentration (here named electrokinetic supercharging (EKS)). Low concentrations (0.2 mg/L) of DNA sample could be detected without fluorescence labeling using a conventional UV detector (at 260 nm). On a single-channel microchip, identification of PCR product was performed by exploiting both external and internal calibration methods. The deviation between the two calibration methods was about 3.6%, and the identified DNA fragment size matched with the predicted size of the template DNA. On the cross microchip the EKS preconcentration has also been achieved when changing the injection reservoir differing from the one used previously. The procedure was computer-simulated and the influence of the voltage applied to two-side reservoirs on sample preconcentration and dilution was also discussed.

Chemistry Letters, 2012

ABSTRACT An open-tubular capillary chromatography system has been developed using a ternary mixed... more ABSTRACT An open-tubular capillary chromatography system has been developed using a ternary mixed solvent solution, i.e., water-hydrophilic/hydrophobic organic solvent mixture as a carrier solution. The system is called "tube radial distribution chromatography (TRDC)." In this study, we tried to carry out the TRDC on a microchip incorporating microchannels. A model analyte solution of isoluminol isothiocyanate (ILITC) and ILITC-labeled bovine serum albumin (BSA) was injected to the double T-junction part (0.5 mm length, ca. 2 nL) on the microchip. The analyte solution was then delivered in the separation microchannel (40 mu m in depth, 100 mu m in width, and 22 cm in length) with a ternary water-acetonitrile-ethyl acetate mixture carrier solution (3:8:4, volume ratio). The model analytes, the ILITC and the labeled BSA were separated through the microchannel, where the carrier solvents were radially distributed in the separation channel generating inner and outer phases. This phenomenon of the solvents is called "tube radial distribution phenomenon (TRDP)." The outer phase functions as a pseudo-stationary phase under laminar flow conditions in the chromatography, i.e., TRDC. Finally, the ILITC and the labeled BSA were eluted in this order and detected with chemiluminescence reaction.

Bulletin of the Chemical Society of Japan, 1989

A highly sensitive fiber-optic immunosensor using an antibody-immobilized optical fiber was devel... more A highly sensitive fiber-optic immunosensor using an antibody-immobilized optical fiber was developed and introduced into a chemiluminescence complex catalyst immunoassay (CLCCIA) which had been reported by the authors in a previous paper. After optimization of the experimental conditions, human serum albumin as model protein was determined by both competitive immunoassay and sandwich immunoassay, using the fiber-optic immunosensor. Human serum albumin could be determined in the concentration range 1×10−4–1×10−1 g dm−3 with a lower limit of 400 pg by competitive immunoassay while in the concentration range 1×10−5–1×10−1 g dm−3 with a lower limit of 40 pg by sandwich immunoassay. The new fiber-optic immunosensor developed by the authors can be characterized as follows: 1) Highly sensitive for the determination of a small amount of protein, 2) applicable to a wide concentration range of protein sample, 3) feasible with a microvolume of sample, 4) suitable for automated operation, and 5) excellent regarding ...

Analytical Sciences, 2000

SEIBUTSU BUTSURI KAGAKU, 2008

Nucleic Acids Symposium Series

The LIGA (Lithographie Galvanoformung Abformung) process using synchrotron radiation lithography ... more The LIGA (Lithographie Galvanoformung Abformung) process using synchrotron radiation lithography is applied to the microfabrication of capillary array electrophoresis (CAE) device. Laser-induced fluorescence detection system for the CAE device has been constructed by the modification of laser confocal fluorescence microscopy. DNA molecules were detected during migrating in the microchannels filled with polymer separation matrices under electric field to optimize the separation conditions for DNA analysis. Based on this observation, we demonstrated that microfabricated CAE device is realized the fast separation of DNA.

SEIBUTSU BUTSURI KAGAKU, 2008

This paper describes the concept of MCE-202 "MultiNA", a new microchip electrophoresis system for... more This paper describes the concept of MCE-202 "MultiNA", a new microchip electrophoresis system for DNA/RNA analysis. MCE-202 "MultiNA" realizes high-throughput and cost-effective analysis with originally developed reusable microchips and reagent kits. Application data for Norovirus detection and meat identification are also presented.

Rapid Communications in Mass Spectrometry, 2006

A system of microchip capillary electrophoresis/electrospray ionization mass spectrometry (mchip-... more A system of microchip capillary electrophoresis/electrospray ionization mass spectrometry (mchip-CE/ESI-MS) for rapid characterization of proteins has been developed. Capillary electrophoresis (CE) enables rapid analysis of a sample present in very small quantity, such as at femtomole levels, at high resolution. Faster CE/MS analysis is expected by downsizing the normal capillary to the microchip (mchip) capillary. Although rapidity and high resolution are advantages of CE separation, electroosmotic flow (EOF) instability caused by the interaction between proteins and the microchannel surface results in low reproducibility in the analysis of basic proteins under neutral pH conditions. By coating the microchannel surface with a basic polymer, polyE-323, basic proteins, which have pI values of over 7.5, could be separated and detected by mchip-CE/MS on quadrupole (Q) and time-offlight (TOF) hybrid instruments. By increasing the cone and collision voltages during the analysis by mchip-CE/ESI-MS of a small protein, some product ions, which contain the sequence information, could also be obtained, i.e., 'top-down' analysis of the protein could be accomplished with this mchip-CE/MS system. To our knowledge, this is the first report of 'top-down' analysis of a protein by mchip-CE/MS. Since it requires a much shorter time and a smaller sample amount for analysis than the conventional liquid chromatography (LC)/ESI-MS method, mchip-CE/MS promises to be suitable for the high-throughput characterization of proteins.

Journal of Chromatography A, 2004

We demonstrate a convenient single-step quantitation technique for double-stranded DNA (dsDNA) fr... more We demonstrate a convenient single-step quantitation technique for double-stranded DNA (dsDNA) fragments in polymerase chain reaction (PCR) products based on microchip capillary electrophoresis (micro-CE)/UV or fluorescence detection. PCR products of polymorphisms on the human Y-chromosome related to spermatogenic failure did not need purification. They were premixed and comigrated with a DNA digest whose concentration was known. Hydroxyethyl cellulose (HEC) dissolved in 5x Tris-borate-EDTA (5x TBE, pH 8.3) was used as a separation matrix in a linear polyacrylamide-coated quartz microchip, while mixed poly(ethyl oxides) (PEOs) of different molar-masses dissolved in 1 x TBE (pH 8.3) containing 1 ng/microl ethidium bromide was used as a separation matrix in an uncoated poly(methyl methacrylate) (PMMA) microchip. Elution profiles were monitored under either real-time linear imaging UV detection in the snapshot mode where the total separation time is fixed, or light-emitting diode (LED) confocal fluorescence detection in the finishline mode where solutes migrate over the same separation length. It is found that, in both modes, a linear relation exists between the peak areas (A) and the multiplication of the digest concentrations (C) and the fragment sizes (L) in a DNA restrictive digest. Using the comigration electropherogram of a single-step experiment, the concentrations of PCR products were directly determined using the A versus LC linear relationship. The sole condition to obey is that the chosen digest has different fragment sizes with the PCR products of interest. This condition is easy to obey, because micro-CE owns high separation ability, and many digests are commercially available. The recovery of the technique was between 98 and 105%. The R.S.D. for chip-to-chip concentration measurements was less than 6.0% (n = 6). Hence, the technique was accurate and reliable for DNA assays.

Journal of Chromatography A, 2003

A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was develo... more A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was developed using a spray nozzle connected to the exit of the separation channel of the microchip. The spray nozzle was attached to the microchip using a polyether ether ketone screw without adhesive, thus allowing easy replaced. Sample injection and electrophoretic separation was performed by control of the voltage only. The analysis of a few basic drugs was performed using the optimized MCE-MS system. The separation was improved by using a high-viscosity separation buffer and a spray nozzle with a small bore size. This system was also applied to the separation of peptides and protein-trypsin digests. Sample adsorption was minimized by adding acetonitrile to the separation buffer when using a quartz microchip.

ELECTROPHORESIS, 2001

We have proposed a field-inversion electrophoresis on a microchip for a shorter effective length,... more We have proposed a field-inversion electrophoresis on a microchip for a shorter effective length, and investigated the external frequency for the DNA analysis based on the field-inversion electrophoresis device. By using the optimized frequency, we demonstrated that the field-inversion electrophoresis has great potentials for the separation of DNA fragments with shorter effective length.

ELECTROPHORESIS, 2003

High-speed electrophoretic analysis of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosacchari... more High-speed electrophoretic analysis of 1-phenyl-3-methyl-5-pyrazolone derivatives of monosaccharides on a quartz microchip with whole-channel UV detection 1-Phenyl-3-methyl-5-pyrazolone (PMP) derivatives of monosaccharides were analyzed by electrophoresis on a quartz microchip with whole-channel UV detection. Rapid separation of PMP derivatives of aldopentoses was achieved by plain-zone electrophoresis in a neutral phosphate buffer with the height equivalent to a theoretical plate at the micrometer level. Zone electrophoresis as borate complexes was also successful for the separation of PMP derivatives of a few aldoses, which were separated within 1 min. Separation by microchip electrophoresis was compared to that by capillary electrophoresis, and the difference was discussed in terms of column efficiency and sample column capacity.

ELECTROPHORESIS, 2001

Microchip electrophoresis for the short-time analysis of amino sugars is described. D-Glucosamine... more Microchip electrophoresis for the short-time analysis of amino sugars is described. D-Glucosamine, D-galactosamine and their reduced forms were labeled with 4-nitro-2,1,3-benzoxadiazole 7-fluoride (NBD-F) at pH 6.0 and the fluorescent derivatives were purified on an octadecyl silica (ODS) gel plate. The derivatives were analyzed by electrophoresis on a microfabricated chip with a 33 mm long separation channel with argon laser-induced fluorescence detection. Under the established conditions, these amino sugarderivatives were well separated from each other within 60 s. Amino sugars of as small an amount as 0.5 fmol could be detected with a signal-to-noise (S/N) ratio of 3, and peak response showed good linearity between at least 0.8 and 8 fmol of samples with a relative standard deviation (RSD) of ca. 4%. This method was also applied to the analysis of amino sugar composition of O-linked glycans released from bovine submaxillary mucin with alkali in the presence of borohydride. The result of amino sugar composition analysis for individual O-glycans fractionated by high-performance liquid chromatography was quite useful for their identification.