University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Toshihiko Imato

Abbrev:
Imato, T.
Other Names:
Address:
Department of Chemical Systems and Engineering, Graduate School of Engineering, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-81, Japan
Phone:
+81-92-642-3569
Fax:
+81-92-642-4134

Citations 25

"Sequential Injection Chemiluminescence Immunoassay For Anionic Surfactants Using Magnetic Microbeads Immobilized With An Antibody"
Talanta 2005 Volume 68, Issue 2 Pages 231-238
RuiQi Zhang, Koji Hirakawa, Daisuke Seto, Nobuaki Soh, Koji Nakano, Takashi Masadome, Kazumi Nagata, Kazuhira Sakamoto and Toshihiko Imato

Abstract: A rapid and sensitive immunoassay for the determination of linear alkylbenzene sulfonates (LAS) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a neodymium magnet. Magnetic beads, to which an anti-LAS monoclonal antibody was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by means of a neodymium magnet and adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an anti-LAS monoclonal antibody on the magnetic beads and the LAS sample and horseradish peroxidase (HRP)-labeled LAS, and was based on the subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The anti-LAS antibody was immobilized on the beads by coupling the antibody with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactic acid film. The antibody immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the neodymium magnet, an LAS solution containing HRP-labeled LAS at constant concentration and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photon counting unit located at the upper side of the flow cell by collecting the emitted light with a lens. A typical sigmoid calibration curve was obtained, when the logarithm of the concentration of LAS was plotted against the chemiluminescence intensity using various concentrations of standard LAS samples (0-500 ppb) under optimum conditions. The time required for analysis is less than 15 min.

"Chemiluminescence Sequential Injection Immunoassay For Vitellogenin Using Magnetic Microbeads"
Talanta 2004 Volume 64, Issue 5 Pages 1160-1168
Nobuaki Soh, Hideshi Nishiyama, Yasukazu Asano, Toshihiko Imato, Takashi Masadome and Youichi Kurokawa

Abstract: A rapid and sensitive immunoassay for the determination of carp vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with a chemiluminescence detector and a samarium-cobalt magnet. An anti-Vg monoclonal antibody, immobilized on magnetic beads, was used as a solid support for the immunoassay. The introduction, trapping and release of the magnetic beads in the flow cell were controlled by a samarium-cobalt magnet and the flow of the carrier solution. The immunoassay was based on a sandwich immunoreaction of anti-Vg monoclonal antibody (primary antibody) on the magnetic beads, Vg, and the anti-Vg antibody labeled with horseradish peroxidase (HRP) (secondary antibody), and was based on a subsequent chemiluminescence reaction of HRP with hydrogen peroxide and p-iodophenol, in a luminol solution. The magnetic beads to which the primary antibody was immobilized were prepared by coupling the primary antibody with the magnetic beads after an agarose-layer on the surface of the magnetic beads was epoxidized. The primary antibody-immobilized magnetic beads were introduced, and trapped in the flow cell equipped with the samarium-cobalt magnet, a Vg sample solution, an HRP-labeled secondary antibody solution and the luminol solution were sequentially introduced into the flow cell based on an SIA programmed sequence. Chemiluminescence emission was monitored by means of a photomultiplier located at the upper side of the flow cell. The optimal incubation times both for the first and second immunoreactions were determined to be 20 min. A concave calibration curve was obtained between Vg concentration and chemiluminescence intensity when various concentrations of standard Vg samples (2-100 ng mL-1) were applied to the SIA system under optimal conditions. In spite of a narrow working range, the lower detection limit of the immunoassay was about 2 ng mL-1.

"Potentiometric Flow Injection Determination Of Manganese(II) By Using A Hexacyanoferrate(III)-hexacyanoferrate(II) Potential Buffer"
Talanta 2003 Volume 60, Issue 1 Pages 177-184
Hiroki Ohura, Yuko Ishibashi, Toshihiko Imato and Sumio Yamasaki

Abstract: A highly sensitive potentiometric flow injection analysis method for the determination of manganese(II), utilizing a redox reaction with hexacyanoferrate(III) in near neutral media containing ammonium citrate is described. The analytical method is based on the detection of the change in potential of a flow-through type redox electrode detector, resulting from the composition change of an [Fe(CN)6]3--[Fe(CN)6]4- potential buffer solution. A linear relationship between the potential change (peak height) and the concentration of manganese(II) was found. Manganese(II) in a wide concentration range from 10^-4 to 10^-7 M could be determined by appropriately altering the concentration of the potential buffer from 10^-3 to 10^-5 M. The lower detection limit of manganese(II) was determined to be 1 x 10^-7 M. The sampling rate and relative standard deviation were 20 h-1 and 1.9% (n=8) for 6 x 10^-6 M manganese(II), respectively. The proposed method was successfully applied to the determination of manganese(II) in actual soil samples obtained from tea fields. Analytical results obtained by the proposed method were in good agreement with those obtained by an atomic absorption spectrophotometric method.

"Spectrophotometric Determination Of Carp Vitellogenin Using A Sequential Injection Analysis Technique Equipped With A Jet Ring Cell"
Talanta 2002 Volume 58, Issue 6 Pages 1123-1130
Nobuaki Soh, Hideshi Nishiyama, Keiko Mishima, Toshihiko Imato, Takashi Masadome, Yasukazu Asano, Youichi Kurokawa, Hisao Tabei and Saeko Okutani

Abstract: A sequential injection analysis (SIA) technique, in which antibody-immobilized microbeads were transferred to a jet ring (JR) cell, was used in determination of carp vitellogenin (Vg). The determination is based on a sandwich immunoassay in which two types of reactions between anti carp Vg antibodies and carp Vg are used. Namely, the antibody for the first reaction step was immobilized on microbeads (Sephadex beads), and an antibody labeled with a horseradish peroxidase (HRP) was used in the second step of the reaction. A mixed solution of hydrogen peroxide and o-phenylenediamine (OPD). was used as the source of the chromophore in the reaction. The microbeads-immobilized antibody, Vg analyte, HRP-labeled anitbody and the color developing solution were introduced automatically into the JR cell of the SIA system in a programmed sequence, and the absorbance of the oxidized OPD product was used to determine the amount of Vg present. The optimal incubation times for the immuno-raction for the first and the second steps were determined at IN and 60 min, respectively, taking into account the sensitivity to the Vg determination. Under these conditions, a good linear correlation was obtained between Vg concentration and the absorbance of the oxidized OPD. The lower detection limit for the determination of Vg was about 5 ng mL-1 in this system. The method developed here represents a simple, accurate method for the determination method of Vg. (C) 2002 Elsevier Science B.V. All rights reserved.
Sequential injection Enzyme

"Potentiometric Flow Injection Analysis Of Concentrated Hydrogen Peroxide By Using An Fe(II)-Fe(III) Redox Potential Buffer Solution"
Talanta 2000 Volume 52, Issue 1 Pages 19-26
Toshihiko Imato, Hiroki Ohura, Sumio Yamasaki and Yasukazu Asano

Abstract: The flow injection analysis of hydrogen peroxide is proposed, using a redox electrode and an Fe(II)-Fe(III) potential buffer solution. Influencing factors, such as the concentrations of Fe(II)-Fe(III) and sulfuric acid in the potential buffer on sensitivity of the proposed method are examined. The analysis of high concentrations of hydrogen peroxide up to similar to 10 M was conducted successfully with relative standard deviation of 0.7%.

"Simultaneous Potentiometric Determination Of ClO3--ClO2-and ClO3--HClO By Flow Injection Analysis Using Fe(III)-Fe(II) Potential Buffer"
Talanta 1999 Volume 49, Issue 5 Pages 1003-1015
Hiroki Ohura, Toshihiko Imato and Sumio Yamasaki

Abstract: A rapid potentiometric flow injection technique for the simultaneous determination of oxychlorine species such as ClO3--ClO2-and ClO3--HClO has been developed, using both a redox electrode detector and a Fe(III)-Fe(II) potential buffer solution containing chloride. The analytical method is based on the detection of a large transient potential change of the redox electrode due to chlorine generated via the reaction of the oxychlorine species with chloride in the potential buffer solution. The sensitivities to HClO and ClO2-obtained by the transient potential change were enhanced 700-800-fold over that using an equilibrium potential. The detection limit of the present method for HClO and ClO2-is as low as 5 x 10^-8 M with use of a 5 x 10^-4 M Fe(III)-1 x 10^-3 M Fe(II) buffer containing 0.3 M KCI and 0.5 M H2SO4. On the other hand, sensitivity to ClO3-was low when a potential buffer solution containing 0.5 M H2SO4 was used, but could be increased largely by increasing the acidity of the potential buffer. The detection limit for ClO3-was 2 x 10^-6 M with the use of a 5 x 10^-4 M Fe(III)-1 x 10^-3 M Fe(II) buffer containing 0.3 M KCI and 9 M H2SO4. By utilizing the difference in reactivity of oxychlorine species with chloride in the potential buffer, a simultaneous determination method for a mixed solution of ClO3--ClO2-or ClO3--HClO was designed to detect, in a timely manner, a transient potential change with the use of two streams of potential buffers which contain different concentrations of sulfuric acid. Analytical concentration ranges of oxychlorine species were 2 x 10^-5-2 x 10^-4 M for ClO3-, and 1 x 10^-6-1 x 10^-5 M for HClO and ClO2-. The reproducibility of the present method was in the range 1.5-2.3%. The reaction mechanism for the transient potential change used in the present method is also discussed, based on the results of batchwise experiments. The simultaneous determination method was applied to the determination of oxychlorine species in a tap water sample, and was found to provide an analytical result for HClO, which was in good agreement with that obtained by the o-tolidine method and to provide a good recovery for ClO3-added to the sample.

"Flow Injection Analysis For Residual Chlorine Using Lead(II) Ion-selective Electrode Detector"
Talanta 1998 Volume 45, Issue 3 Pages 575-581
Aki Sakaia, Akihide Hemmia, Hiromitsu Hachiyaa, Fumie Kobayashia, Satoshi Itoa, Yasukazu Asanoa, Toshihiko Imatob,*, Yoshito Fushinukic and Isao Taniguchid

Abstract: A flow injection analysis (FIA) system for residual Cl in tap water uses a Pb(II) ion-selective electrode (ISE) detector and it is based on the specific response of the Pb(II)-ISE to residual Cl. The FIA system consists of a millivolt meter, a peristaltic pump, a Pb(II)-ISE detector and a recorder. A linear working curve between peak height and concentration. of residual Cl was obtained for 0.1-1 mg/L. The relative standard deviation for repeated injections of 0.2 mg/L residual Cl sample was 2%. The regression line and its correlation factor between the conventional o-tolidine colorimetric method and this method were Y = 0.75X+0.17 and 0.967, respectively, for this determination.
Chlorine, residual Water Electrode Indirect Method comparison

"Potentiometric Flow Injection Determination Of Amylase Activity By Using Hexacyanoferrate(III)-hexacyanoferrate(II) Potential Buffer"
Talanta 1998 Volume 45, Issue 3 Pages 565-573
Hiroki Ohuraa, Toshihiko Imatob,*, Yasukazu Asanoc and Sumio Yamasakia

Abstract: A highly sensitive potentiometric flow injection determination of amylase activity was carried out, utilizing a redox reaction of hexacyanoferrate(III) in alkaline media with reducing sugar as product of the enzymatic hydrolysis reaction of starch with amylase. The analysis method is based on the potential change detection of a flow-through type redox electrode detector due to the composition change of a [Fe(CN)6]3--[Fe(CN)6]4- potential buffer solution, which is caused by the redox reaction with the product of the enzymatic reaction. A linear relationship exists between the potential change (peak height) and the activity of amylase. Amylase of a wide activity range from 2.5 x 10^-2 to 1.2 x 10^-4 U mL-1 can be determined by the changing the concentrations of the [Fe(CN)6]3--[Fe(CN)6]4- potential buffer from 10^-3 to 10^-5 M. The lower detection limit of amylase activity is 6.0 x 10^-5 U mL-1. The sampling rate and relative standard deviation are 15 h-1 and 0.9% (n = 5) for 3.8 x 10^-3 U mL-1 of amylase. The present method was successfully applied to determine amylase activity in real samples (commercial digestive medicines) with an accuracy of 4% compared with analytical results obtained using the present method with those achieved using the conventional titration method.
α-Amylase Pharmaceutical Potentiometry Redox Method comparison Indirect

"Potentiometric Flow Injection Determination Of Trace Hydrogen Peroxide Based On Its Induced Reaction In Iron(III)-iron(II) Potential Buffer Containing Bromide And Molybdenum(VI)"
Talanta 1996 Volume 43, Issue 6 Pages 943-950
Nobuhiko IshibashiHiroki Ohuraa, Toshihiko Imatob,* and Sumio Yamasakia

Abstract: Sample was injected into a carrier stream (1 ml/min) of water which then merged with a reagent stream (1 ml/min) of 0.1 mM Fe(III)/Fe(II) buffer solution containing 0.4 M NaBr, 0.5% Mo(VI) and 1 M H2SO4. The resultant stream passed through a reaction coil (100 cm) to a flow-through oxidation-reduction potential electrode detector with a Ag/AgCl reference electrode and a Au-plates oxidation-reduction potential electrode. The detection limit was 0.4 µM-H2O2 with a RSD (n = 6) of 0.6% for 4 µM-H2O2. The method was applied to the determination of H2O2 in rain with recoveries of 95.8-104.1%.
Hydrogen peroxide Rain Environmental Potentiometry

"Flow Injection Titration Using Reaction With Buffer Solution"
J. Flow Injection Anal. 1995 Volume 12, Issue 1 Pages 145-166
Toshihiko IMATO

Abstract: The methodology of flow injection titration of acids, bases, metals and redox compounds using a buffer solution with respect to pH, free metal ion concentration or redox potential has been proposed and applications of the proposed method to neutralization titration, chelate titration and redox titration are reviewed. The method is based on detection of variation in a property of the buffer solution due to a reaction with a sample injected in the buffer stream potentiometrically or spectrophotometrically. pH buffer solution and a glass electrode are utilized for determination of concentrated acids and bases, total amino acids in the Sake (Japanese rice wine). pH titration in non-aqueous solvent is applied to the determination of total alkalinity of lubrication oil and saponification values in food oil.
Titrations Buffer

"Liposome Flow Injection Immunoassay"
J. Flow Injection Anal. 1992 Volume 9, Issue 2 Pages 204-204
T. Imato

Abstract: Brief introduction to liposome immunoassays by FIA
Immunoassay

"Flow Injection Analysis Of Hydrogen Peroxide In The Bleaching Solution Using A Flow-through Type ORP Electrode Detector"
J. Flow Injection Anal. 1992 Volume 9, Issue 2 Pages 187-194
Yoshio MAESHIMA, Takuo INUI, Aki SAKAI*, Akihide HENMI*, Satoshi ITO, Yasukazu ASANO and Toshihiko IMATO

Abstract: Bleach (5 µL) was injected into a stream of water (0.9 mL min-1) which was subsequently merged with a stream (0.9 mL min-1) of 0.02 M Fe(III) - 0.02 M Fe(II) - 1.2 M H2SO4 followed by detection with a flow-through type ORP electrode detector. The concentration of H2O2 was determined by measuring the potential change of the detector, which was observed as a peak-shaped signal. Sample throughput was 15 h-1. The results obtained compared well with those of a standard titrimetric method.
Hydrogen peroxide Commercial product Electrode Method comparison

"Potentiometric Flow Injection Analysis Of Redox Compounds Using Redox Potential Buffer"
J. Flow Injection Anal. 1991 Volume 8, Issue 1 Pages 2-20
Hiroki OHURA, Toshihiko IMATO, Sumio YAMASAKI, Nobuhiko ISHIBASHI

Abstract: A review is presented, with 38 references, on the use of the cited technique for the determination of water, oxalic acid, hydrazine, BrO3-, ClO-, non-reducing and reducing sugars, and ethanol.
Bromate Ethanol Hydrazine Hypochlorite Oxalic acid Sugars, nonreducing Sugars, reducing Water Potentiometry Buffer Redox Review

"Flow Injection Analysis Of Metal Ions By Using Metal Buffer Solutions Containing Metal Indicators"
J. Flow Injection Anal. 1989 Volume 6, Issue 2 Pages 160-168
Toshihiko Imato, Kazuya Ishii, Ko Saitoh, Yuji Kawabata and Nobuhiko Ishibashi

Abstract: Three flow injection analysis methods are described. In method (i), Zn is determined spectrophotometrically by injection of a 100 µL portion of sample into a carrier stream of water to mix with a Zn buffer stream containing 20 µM-xylenol orange, 10 mM nitrilotriacetic acid and 5 mM Zn (NO3)2 of pH 5.75 in the flow injection analyzer., followed by detection at 578 nm. In method (ii), Zn is determined fluorimetrically by injection of a 200 µL portion of sample into a carrier stream of water to react with a mixture containing 1 mM Zn (NO3)2, 2 mM nitrilotriacetic acid and 20 µM-8-hydroxyquinoline-5-sulfonic acid at pH 6 followed by detection at 525 nm (excitation at 375). In method (iii), La is determined spectrophotometrically by injection of a 200 µL portion of the sample into a carrier stream of water to react with a La buffer consisting of 20 µM-arsenazo III, 5 mM EDTA and 2.5 mM La(NO3)3 of pH 4.47, followed by detection at 655 nm. Calibration graphs were rectilinear up to 5 mM of analyte solution The methods can also be used for the determination of other heavy and rare-earth metals.
Metals, heavy Metals, rare earth Zinc Lanthanum Spectrophotometry Fluorescence Buffer Method comparison 8-hydroxyquinoline-5-sulfonic acid

"Flow Injection Analysis Bibliography (10)"
J. Flow Injection Anal. 1988 Volume 5, Issue 2 Pages 141-156
Toshihiko Imato and Hiroki Ohura

Abstract: Refs 1100-1247 (148 citations)
Bibliography

"Flow Injection Analysis Bibliography (9)"
J. Flow Injection Anal. 1988 Volume 5, Issue 1 Pages 31-45
Toshihiko Imato and Hiroki Ohura**

Abstract: Refs 953-1099 (147 citations)
Bibliography

"Flow Injection Analysis Bibliography (8)"
J. Flow Injection Anal. 1987 Volume 4, Issue 2 Pages 146-164
Toshihiko lmato* and Hiroki 0hura**

Abstract: Refs 771-952 (182 citations)
Bibliography

"Flow Injection Analysis Bibliography (7)"
J. Flow Injection Anal. 1987 Volume 4, Issue 1 Pages 40-57
Toshihiko Imato and Hiroki 0hura

Abstract: Refs 598-770 (173 citations)
Bibliography

"Flow Injection Analysis Of Organic Acids And Amino Acids In Sake By Using PH-sensitive Glass Electrode And Acid Base Buffer Solution"
J. Flow Injection Anal. 1986 Volume 3, Issue 2 Pages 103-111
Toshihiko Imato, Chie Azemori, Yasukazu Asano and Nobuhiko Ishibashi

Abstract: To determine organic acids, the sample solution was injected into a stream of water, which was merged with a neutral H2PO4- - HPO42- buffer solution The pH change caused by acid - base reaction between the acid and HPO42- was detected with a flow-through pH electrode. Amino-acids were determined by injecting the sample into a stream of water, which was merged with formaldehyde to convert the analytes into stronger acids; the resulting solution was merged with alkaline phosphate buffer solution and the change in pH was monitored as before. Results correlated well with those of conventional neutralization titration.
Carboxylic acids Amino Acids Sake Wine Clinical analysis Electrode Potentiometry

"Electrochemical Sandwich Immunoassay For Vitellogenin By Sequential Injection Analysis Using Antibody Immobilized Magnetic Microbeads"
Electroanalysis 2006 Volume 18, Issue 13-14 Pages 1297-1305
Koji Hirakawa 1, Masaaki Katayama 1, Nobuaki Soh 1, Koji Nakano 1, Hiroki Ohura 2, Sumio Yamasaki 2, Toshihiko Imato 1 *

Abstract: A rapid and sensitive sandwich immunoassay based on a sequential injection analysis (SIA) for the determination of carp vitellogenin (Vg) is described. The SIA system was constructed from a syringe pump, a multiposition valve, a flow-through type immunoreaction cell equipped with a magnet and an amperometric detector. Magnetic microbeads immobilized with an anti-Vg monoclonal antibody (primary antibody) were used as a solid support. The primary antibody was immobilized on magnetic microbeads by coupling the primary antibody with a polylactic acid-layer, which was coated on the surface of the magnetic beads, after activated with N-hydroxysuccinimide. The introduction, trapping and flushing out of the magnetic microbeads in the immunoreaction cell were controlled by the magnet and the flow of the carrier solution. After the primary antibody-immobilized magnetic beads were introduced and trapped in the immunoreaction cell, a Vg sample solution, an alkaline phosphatase (AP)-labeled anti-Vg polyclonal antibody (secondary antibody) solution and a p-aminophenyl phosphate (PAPP) solution were sequentially introduced into the immunoreaction cell based on an SIA programmed sequence. Vg was determined by the electrochemical detection of p-aminophenol (PAP), an enzymatic product of PAPP via the action by AP labeled on the secondary antibody. A solution containing PAP, which was generated in the immunoreaction cell and transiently held in a holding coil, was transported to the amperometric detector and the oxidation current of PAP on a working electrode applied at +0.20 V was measured. A sigmoidal calibration curve was obtained in the concentration range from 1 ppb to 500 ppb in a plot of oxidation current against the logarithm of the Vg concentration. The lower detection limit of the immunoassay was about 2-3 ppb. The time required for an analysis was ~15 min/sample.

"Polymer-based Ion-selective Electrode And Its Application To Flow Analysis"
Bunseki 1989 Volume 1989, Issue 9 Pages 758-762
Imato, T.

Abstract: A review is presented with 7 references.
Electrode Electrode Review

"Development Of Chemical Sensors And Their Application To Flow Analysis Systems"
Bunseki Kagaku 2005 Volume 54, Issue 12 Pages 1123-1136
Toshihiko IMATO

Abstract: Flow analysis has many advantages concerning sensitivity, accuracy, repeatability and analytical throughput etc, compared with a batchwise analysis. The flow-based method makes the involved analytical processes automatic and rapid. Therefore, the combination of a chemical sensor with the flow method enhances the performances of the chemical sensor. Especially, potentiometric detection using ion-selective electrodes has been widely used in flow analysis due to its features, simplicity in analytical operation and wide dynamic range in analysis. This paper reports on several chemical sensors applied to flow systems that we have engaged so far concerning: (1) Liquid membrane type ion-selective electrodes, such as nitrate, vitamin Bi, tetrafluoroborate and surfactants sensitive electrodes based on an oleophilic anion exchange resin membrane and a hydrophobic ion exchanger. (2) Flow titration by using both a buffer solution and its corresponding electrode, such as a pH glass electrode with a pH buffer, a copper(II) ion-selective electrode with a metal ion buffer solution and a redox electrode with a potential buffer solution. (3) Surface plasmon resonance sensors for succarides and some endocrine disrupting chemicals based on a boronic acid polymer membrane and antigen or antibody immobilized membrane. (4) Sequential injection analysis combined with beads injection technique for vitellogenin as biomarker for assessing the pollution of environment in hydrosphere.

"Electrochemical Immunoassay For Vitellogenin Based On Sequential Injection Using Antigen-immobilized Magnetic Microbeads"
Anal. Sci. 2006 Volume 22, Issue 1 Pages 81-86
Koji Hirakawa, Masaaki Katayama, Nobuaki Soh, Koji Nakano And Toshihiko Imato

Abstract: A rapid and sensitive immunoassay for the determination of vitellogenin (Vg) is described. The method involves a sequential injection analysis (SIA) system equipped with an amperometric detector and a neodymium magnet. Magnetic beads, onto which an antigen (Vg) was immobilized, were used as a solid support in an immunoassay. The introduction, trapping and release of magnetic beads in an immunoreaction cell were controlled by means of the neodymium magnet and by adjusting the flow of the carrier solution. The immunoassay was based on an indirect competitive immunoreaction of an alkaline phosphatase (ALP) labeled anti-Vg monoclonal antibody between the fraction of Vg immobilized on the magnetic beads and Vg in the sample solution. The immobilization of Vg on the beads involved coupling an amino group moiety of Vg with the magnetic beads after activation of a carboxylate moiety on the surface of magnetic beads that had been coated with a polylactate film. The Vg-immobilized magnetic beads were introduced and trapped in the immunoreaction cell equipped with the neodymium magnet; a Vg sample solution containing an ALP labeled anti-Vg antibody at a constant concentration and a p-aminophenyl phosphate (PAPP) solution were sequentially introduced into the immunoreaction cell. The product of the enzyme reaction of PAPP with ALP on the antibody, p-aminophenol, was transported to an amperometric detector, the applied voltage of which was set at +0.2 V vs. an Ag/AgCl reference electrode. A sigmoid calibration curve was obtained when the logarithm of the concentration of Vg was plotted against the peak current of the amperometric detector using various concentrations of standard Vg sample solutions (0 - 500 ppb). The time required for the analysis is less than 15 min.

"Spectrophotometric Flow Injection Analysis Of The Total Base Number In Lubricants By Using Acid-base Buffers"
Anal. Chim. Acta 2001 Volume 438, Issue 1-2 Pages 83-92
Keiko Jyonosono, Toshihiko Imato, Noriyuki Imazumi, Masayuki Nakanishi and Jun-ichi Yagi

Abstract: A spectrophotometric FIA method for the determination of the total base number (TBN) in a lubricant was proposed, which involved using an acid-base buffer solution prepared with a nonaqueous solvent. This method is based on measurements of the absorbance change of an indicator contained in the acid-base buffer solution, which is generated due to a neutralization reaction of base in the lubricant with the buffer acid. The sample injected into a stream of a nonaqueous solvent, toluene/H2O/2-propanol (52/1/47 v/v/v), was merged with a stream of perchloric acid (HClO4) solution, and then neutralized with HClO4. An excess of HClO4 was subsequently merged with a stream of tetrabutylammonium salt of trifluoroacetic acid (TFA(.)TBA) solution containing an indicator (m-cresol purple), which pK(a) value was found to be similar to pK(a) value of TFA in the present mixed nonaqueous solvent. The reaction of the excess HClO4 with TFA(.)TBA gave rise to the composition change of the acid-base buffer solution, TFA/TFA(.)TBA. Since the indicator, m-cresol purple, behaves similarly to the buffer component, the change in the concentration ratio of TFA/TFA(.)TBA can be determined by the measurement of the absorbance change of the indicator. The absorbance changes were monitored with a spectrophotometric detector. The sensitivity of the proposed method for several kinds of basic compounds, which were often added to lubricant, was nearly identical irrespective of the basicity of the compounds. The proposed method was successfully applied to the determination of the total base number in lubricant.

"Sensitivity Enhancement By Potentiometric Flow Injection Analysis Based On Redox Reaction With An Iron(III) - Iron(II) Buffer"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 405-410
Nobuhiko Ishibashi, Toshihiko Imato*, Sumio Yamasaki and Hiroki Ohura

Abstract: For the determination of oxidizing species, the sample solution (200 µL) is injected into water as carrier and the stream is mixed with a reagent solution containing 0.01 M Fe(III) - 0.01 M Fe(II), 0.4 M NaBr and 1.2 M H2SO4 in a 100-cm reaction coil. The resulting solution passes to an oxidation - reduction potential electrode detector (cf. Ibid., 1988, 214, 349) for potentiometric measurement. The transient potential change is rectilinearly related to the concentration. of Cr2O72-, BrO3-, ClO2-, H2O2 or O3 (sensitivities tabulated). Detection limits for the first three species are 0.3 µM, 0.05 µM and 0.1 µM, respectively; the sensitivity towards H2O2 is enhanced by adding 0.5% of (NH4)6Mo7O24 to the reagent solution. A sampling rate of 40 h-1 is attainable. Highly sensitive potentiometric flow injection analysis for oxidative species such as bromate, chlorite, dichromate, hydrogen peroxide and ozone is described, using an Fe(III)-Fe(II) potential buffer containing bromide. The method is based on detection of large transient potential changes of an oxidation-reduction potential electrode which appear in short period after mixing a sample with the potential buffer. This large transient potential change is due to bromine generated by the reaction of the sample with bromide in the potential buffer. Anal. sensitivities obtained by the transient change of potential are enhanced 25-350-fold compared with that using the change in equilibrium. potential. Detection limits of 5 x 10^-8 M for bromate, 1 x 10^-7 M for chlorite and 3 x 10^-7 M for dichromate were obtained by using a 0.01 M Fe(III)-0.01 M Fe(II) potential buffer containing 0.4 M NaBr and 1.2 M H2SO4. For the determination of hydrogen peroxide, the addition of ammonium molybdate to the potential buffer accelerates the generation of bromine caused by the reaction of hydrogen peroxide with bromide and thus enhances the sensitivity.
Dichromate Bromate Chlorite Hydrogen peroxide Potentiometry Redox