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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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Michio Zenki

Abbrev:
Zenki, M.
Other Names:
Address:
Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 7008530, Japan
Phone:
+81 86 256 9446
Fax:
+81 86 256 9757

Citations 16

"Clean Analytical Methodology For The Determination Of Lead With Arsenazo III By Cyclic Flow-injection Analysis"
Talanta 2005 Volume 68, Issue 2 Pages 281-286
Michio ZenkiCorresponding Author Contact Information, E-mail The Corresponding Author, Kazuyoshi Minamisawa and Takashi Yokoyama

Abstract: A clean analytical methodology, where the sample determined and the reagent used are both toxic, has been proposed. A cation exchange mini-column was incorporated after the flow-through cell for on-line regeneration of the main reagent and the accumulation of heavy metal ions. The method involves the spectrophotometric determination of lead with Arsenazo III, the accumulation of lead onto the cationic exchanger, and subsequent regeneration of the chromogenic reagent, which makes the system reversible and the reagents reusable. The developed method provides a satisfactory way to cut down on the toxic reagent consumption and the produced volume of waste, an important step towards the zero emissions research initiative concept. The excellent repeatability and reproducibility, and the simplicity of this method are well suited for continuous measurements. The method was successively applied to the assay of lead in high-octane gasoline. © 2005 Elsevier B.V. All rights reserved.

"Repetitive Determination Of Ascorbic Acid Using Iron(III)-1.10-phenanthroline-peroxodisulfate System In A Circulatory Flow Injection Method"
Talanta 2004 Volume 64, Issue 5 Pages 1273-1277
Michio Zenki, Akihiro Tanishita and Takashi Yokoyama

Abstract: Ascorbic acid (AA) could be determined in large quantities of a co-existing oxidant. The incorporation of an on-line reagent regeneration step based on redox reaction eliminates the baseline drift in the procedure. This makes it possible to adopt a circulatory flow injection method (cyclic FIA) and to determine AA repetitively. The method is based on the reduction of iron(III) to iron(II) by the analyte, the reaction of the produced iron(II) with 1,10-phenanthroline (phen) in a weak acidic medium to form a colored complex, and the subsequent oxidation reaction of iron(II) to iron(III) by the co-existing peroxodisulfate. A solution (50 ml) of 3.0 x 10^-4 mol L-1 ferric chloride, 9.0 x 10^-4 mol L-1 phen and 5.0 x 10^-2 mol L-1 ammonium peroxodisulfate in acetate buffer (0.2 mol l-1, pH 4.5) is continuously circulated at a constant flow rate of 1.0 mL min-1. Into this stream, an aliquot (20 µl) of the sample solution containing AA is quickly injected by means of a six-way valve. The complex formed is monitored spectrophotometrically (at 510 nm) in the flow system. The stream then returns to the reservoir after passing through a time-delay coil (50 m). The iron(II)-(phen)3 complex is oxidized to iron(III)-(phen)3 complex by peroxodisulfate which exists excessively in the circulating reagent solution. The proposed method allows as many as 300 repetitive determinations of 15 mg L-1 AA with only 50 mL reservoir solution. The contents of AA in commercial pharmaceutical products were analyzed to demonstrate the capability of the developed system.

"Repetitive Determination Of Chloride Using The Circulation Of The Reagent Solution In Closed Flow-through System"
Talanta 2002 Volume 58, Issue 6 Pages 1055-1061
Michio Zenki and Yuko Iwadou

Abstract: The precipitation reaction of silver chloride (AgCl) is carried out in a large amount of ammonia (NH3). This makes possible to adopt a closed-loop flow injection (FI) system and to determine chloride repetitively. A solution of 30 mmol L-1 silver nitrate and 80 mmol L-1 NH3 in a single reservoir (250 ml) is continuously circulated through the flow cell at a flow rate of 2.0 mL mL-1. The chloride containing sample (100 µL) was introduced into this reagent solution by means of six-way valve. AgCl precipitates formed in the sample zone are monitored spectrophotometrically (at 500 nm) in the flow system. After passing through the flow cell, the excess NH3 in the circulating reagent solution dissolves AgCl precipitates and the stream then returns to the reservoir. Various variables of the FI system were optimized and a study of interfering ions was also carried out. A linear calibration graph was obtained from 3.0 to 30 mg L-1 chloride. Two hundred repetitive injections of 5.0 mg L-1 chloride into the circulating reagent solution have shown unchanged baseline and good reproducibility. The method was successfully applied to the determination of chloride in tap, natural and the reference waters. (C) 2002 Elsevier Science B.V. All rights reserved.

"Flow Injection Methods For Boron Determination"
J. Flow Injection Anal. 1998 Volume 15, Issue 1 Pages 17-24
Zenki, M.

Abstract: A review with 36 references. Boron is one of the most difficult elements to determine quant. This review summarized the methods for the determination of boron including flow injection anal.-colorimetry, fluorimetry and methods of inductively coupled plasma atomic emission spectrometry and mass spectrometry.
Boron Spectrophotometry Fluorescence Mass spectrometry Spectrophotometry Review

"FIA Using Electroosmosis Flow"
J. Flow Injection Anal. 1995 Volume 12, Issue 1 Pages 98-99
Zenki, M.

Abstract: No abstract available
Electroosmotic flow

"Flow Injection Spectrophotometric Determination Of Calcium In Rain And Snow With Chlorophosphonazo III"
Fresenius J. Anal. Chem. 1990 Volume 338, Issue 6 Pages 707-709
Michio Zenki, Kikuko Ohmuro and Kyoji Tôei

Abstract: A two-fold manifold (diagram given) is used for the determination of Ca in rain and snow based on the complex formation with chlorphosphonazo III in the presence of 0.01 M oxalate (pH 2.8). Barium, Sr and rare-earth metals interfered. Under optimum conditions, the calibration curve was rectilinear up to 1.2 ppm Ca and the detection limit was 0.01 ppm for 120 µL of sample. The coefficient of variation for 0.4 and 1.0 ppm Ca were 0.354 and 0.352%, respectively. Results agreed well with those obtained by AAS.
Calcium Rain Snow Spectrophotometry pH Interferences Method comparison Detection limit Optimization

"Repeated Use Of A Reagent Solution As A Model Of Fe(II)-1,10-phenanthroline In Cyclic-flow Injection Analysis"
Bunseki Kagaku 2001 Volume 50, Issue 5 Pages 329-333
Michio Zenki, Shuhei Tanaka and Yuko Iwadou

Abstract: The use of a closed-loop flow system in flow injection analysis (FIA) allows the recycling of any reagents which are present in excess. The spectrophotometric determination of iron(II) with 1,10-phenanthroline was chosen as a model system. The reagent solution was circulated through a photometric cell at a flow rate 1.5 ml/min, and signals at 510 nm were recorded on a strip chart recorder. To estimate the recycling of the reagent solution, Fe(II) standard solutions (0 similar to 10 ppm) were injected in triplicate for calibration, a 5 ppm Fe(II) standard solution was injected 100 times in sequence, and calibration followed again. The effect of the reservoir mixture volume, the concentration of the Fe(II) standard solution and 1,10-phenanthoroline, and the injection volume were investigated. The typical reservoir mixture, which consisted of 0.1% o-phen and ascorbic acid and 0.02 M acetate buffer (pH 5.0), allowed consecutive determinations of 5 ppm Fe(II) more than 100 times.

"Spectrophotometric Flow Injection Analysis Measurement Of Ethanol Content In Distilled Alcoholic Beverages Using Sulfonazo-III-barium Complex"
Bunseki Kagaku 1990 Volume 39, Issue 10 Pages 597-599
Zenki, M.;Sakita, E.;Hironaka, T.;Toei, K.

Abstract: Sample solution (180 µL) was injected into a carrier stream (0.5 mL min-1) of water and reacted with a reagent solution (0.5 mL min-1) of 0.01 M acetate buffer (pH 3.5) containing 0.1 mM sulfonazo III and 40 µM of Ba2+ with detection at 640 nm. The calibration graph was rectilinear up to 50% of ethanol. Coefficients of variation (n = 5) for 10 and 30% ethanol were 0.51 and 0.87%, respectively. The results obtained agreed well with certified values.
Ethanol Beverage Spectrophotometry Buffer pH Calibration Reference material Indirect

"Determination Of Calcium By FIA With Glyoxal Bis-(2-hydroxyanil)"
Bunseki Kagaku 1989 Volume 38, Issue 9 Pages T129-T133
Zenki, M.;Kogawa, H.;Nose, K.;Toei, K.

Abstract: Calcium was determined in natural waters by the cited method. Glyoxal bis-(2-hydroxyanil) reagent (0.05%), 0.2 M NaOH and water were used as reagent, buffer and carrier solution, respectively, and were propelled (0.6 mL min-1) by plunger micropumps. Sample solution (290 µL) was injected into the carrier solution, mixed with reagent solution and then passed to a PTFE reaction coil (8 m x 0.5 mm). The absorbance of the red solution obtained was measured at 520 nm. The calibration graph was rectilinear for up to 1.2 ppm of Ca and the detection limit was 5 ppb. The coefficient of variation (n = 10) were 1.2 and 0.22% at 0.4 and 1 ppm of Ca, respectively. Results agreed well with those obtained by AAS. Calcium was determined in natural waters by the cited method. Glyoxal bis-(2-hydroxyanil) reagent (0.05%), 0.2 M NaOH and water were used as reagent, buffer and carrier solution, respectively, and were propelled (0.6 mL min-1) by plunger micropumps. Sample solution (290 µL) was injected into the carrier solution, mixed with reagent solution and then passed to a PTFE reaction coil (8 m x 0.5 mm). The absorbance of the red solution obtained was measured at 520 nm. The calibration graph was rectilinear for up to 1.2 ppm of Ca and the detection limit was 5 ppb. The coefficient of variation (n = 10) were 1.2 and 0.22% at 0.4 and 1 ppm of Ca, respectively. Results agreed well with those obtained by AAS.
Calcium Environmental Buffer Calibration Detection limit

"Indirect Spectrophotometric Determination Of Fluoride By FIA Using Arsenazo III - Uranium Complex"
Bunseki Kagaku 1989 Volume 38, Issue 9 Pages 424-428
Zenki, M.;Sai, K.;Ye, Y.;Toei, K.

Abstract: Lanthanum (III), Th(IV) and U(VI) complexes of arsenazo III were evaluated as reagents. Optimum arsenazo III concentration, metal ion concentration, pH, reaction coil length and sample volume were investigated. The U(VI) complex was preferred. A 48 µM-arsenazo III solution (pH 2.8) was used as reagent solution Sample solution (196 µL) was injected into water (carrier solution); PTFE tubing (20 cm x 0.5 mm) was used as the reaction coil. The absorbance was measured at 606 nm. Cation interference was eliminated with use of a cation-exchange column. The calibration graph was rectilinear up to 1.5 ppm of F- and the detection limit was 50 ppb. The coefficient of variation was 0.45% for 0.5 ppm of F- (n = 10). The method was applied in determination of F- in well waters. Lanthanum (III), Th(IV) and U(VI) complexes of arsenazo III were evaluated as reagents. Optimum arsenazo III concentration, metal ion concentration, pH, reaction coil length and sample volume were investigated. The U(VI) complex was preferred. A 48 µM-arsenazo III solution (pH 2.8) was used as reagent solution Sample solution (196 µL) was injected into water (carrier solution); PTFE tubing (20 cm x 0.5 mm) was used as the reaction coil. The absorbance was measured at 606 nm. Cation interference was eliminated with use of a cation-exchange column. The calibration graph was rectilinear up to 1.5 ppm of F- and the detection limit was 50 ppb. The coefficient of variation was 0.45% for 0.5 ppm of F- (n = 10). The method was applied in determination of F- in well waters.
Fluoride Environmental Spectrophotometry Column Calibration Detection limit Complexation Interferences Indirect

"Repetitive Determination Of Chemical Oxygen Demand By Cyclic Flow Injection Analysis Using On-line Regeneration Of Consumed Permanganate"
Anal. Sci. 2006 Volume 22, Issue 1 Pages 77-80
Michio Zenki, Satoru Fujiwara And Takashi Yokoyama

Abstract: A cyclic flow injection analysis (cyclic FIA) for the repetitive determination of chemical oxygen demand (COD) was developed. The acidic KMnO4 method was carried out by adopting a single-line circulating flow system. The oxidant (KMnO4) consumed by the oxidation of organic substances was regenerated and reused repeatedly, resulting in an extreme reduction of hazardous wastes. Only 50 mL of the reagent carrier solution containing 0.2 mM KMnO4 and 1 mM HIO4 in 0.8 M H2SO4 solution was continuously circulated through the system. The KMnO4 could play two roles: acting as an oxidant of the organic substances and/or a spectrophotometric reagent. The co-existing HIO4 acted as a regenerator of KMnO4, which made it possible to recycle the system repeatedly. Under two different digestions (70 and 130°C), 50 repetitive determinations of standard sodium oxalate (6.5 mg COD L-1) and D-glucose (7.2 mg COD L-1) were skillfully carried out with a slightly decreased baseline. The analytical frequency was 30 samples per hour for COD determination. The proposed method saved consumption of the used reagents, KMnO4 and H2SO4, and thus these wastes were extremely reduced. The obtained COD values with the proposed method were co-related with those provided by the manual standard method, but were fairly low owing to the insufficient digestion step.

"Cyclic Flow-Injection Analysis For The Repetitive Determination Of Zinc With 2-(5-Bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol And EDTA"
Anal. Sci. 2005 Volume 21, Issue 5 Pages 517-520
Michio ZENKI, Makiko IDESHIMA, Miwa TANIGUCHI, Ayako KATOH, and Takashi YOKOYAMA

Abstract: A circulatory flow-injection method (cyclic FIA) for the repetitive determination of zinc has been proposed. The procedure involves the use of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (5-Br-PAPS) together with EDTA as a reagent carrier solution, which is recycled in a single-line flow system via a reservoir. The formed 5-Br-PAPS-Zn(II) complex was measured spectrophotometrically at 552 nm, and the signal intensity corresponded to the zinc concentration. After passing through a flow-through cell, the carrier stream then returned to the reservoir, and the main reagent, 5-Br-PAPS, was successfully regenerated by a ligand-exchange reaction with EDTA, allowing the repetitive determination of zinc. The calibration curve for zinc was linear in the concentration range from 0.4 to 10.0 mg L-1 with a correlation coefficient of 0.9995 (n = 6). The detection limit of this method was 0.02 mg L-1 (S/N = 3). This method allowed as many as 300 repetitive determinations of 2.0 mg L-1 zinc solution with only 100 mL of the circulating carrier solution, providing a reduction in the consumption of reagents and an elimination of waste, an important approach towards clean chemistry.

"Repetitive Determination Of Calcium Ion And Regeneration Of A Chromogenic Reagent Using Chlorophosphonazo III And An Ion Exchanger In A Circulatory Flow Injection System"
Anal. Sci. 2002 Volume 18, Issue 10 Pages 1137-1140
Michio Zenki, Tomoko Masutani And Takashi Yokoyama

Abstract: The spectrophotometric determination of Ca2+ with chlorophosphonazo III (CPN) has been carried out by a circulatory flow injection (FI) method. A cation-exchange mini-column for the on-line regeneration of the main reagent was incorporated in this FI system, allowing a repetitive determination of Ca2+. A solution of 4.0 x 10^-5 M CPN in a 0.05 M acetate buffer (pH 5.0) in a single reservoir (50 ml) was continuously circulated at a constant flow rate of 1.5 mL min-1. Into the stream, an aliquot (20 µL) of a sample containing Ca2+ was quickly injected by means of a 6-way valve. The complex formed was monitored spectrophotometrically at 670 nm in the flow system. Then, the stream passed through a cation-exchange column, which was introduced after the flow-through cell. A successful ligand-exchange reaction of Ca2+ between the CPN reagent and a cation exchanger, as well as a simultaneous regeneration of the free reagent took place. The stream then returned to the reservoir. The regeneration and recycling of the CPN reagent allowed as many as 300 repetitive determinations of 2.5 mg L-1 Ca2+ solutions with the same 50 mL circulating solution.

"Flow Injection Analysis Of Copper(II) With PAR In The Presence Of EDTA"
Anal. Sci. 2002 Volume 18, Issue 10 Pages 1077-1079
Michio ZENKI, Yuko IWADOU and Takashi YOKOYAMA

Abstract: The aim of this study was to reveal the color reaction of metal ions with an organic reagent in the presence of a complexing agent (EDTA) and to develop a cyclic FIA for the repetitive determination of metal ions. A famous spectrophotometric reagent, PAR, was chosen because of its water solubility compared to that of, 1-(2-pyridylazo)-2-naphthol (PAN),1-4 and the copper(II)-PAR-EDTA system has been employed as a model for a cyclic FIA. The proposed method allows as many as 100 repetitive determinations of 2.5 ppm copper(II) with only a 100 mL reservoir solution. The use of a cyclic FIA provides a better utilization of the reagents, while minimizing the waste, decreasing the operating cost and shortening the determination time. This is one approach to the ZERI (zero emissions research initiative) concept.

"Flow Injection Determination Of Trace Amounts Of Hydrogen Peroxide With Thio-Michler's Ketone"
Anal. Sci. 1990 Volume 6, Issue 7 Pages 149-150
K. TOEI, T. TAMARU and M. ZENKI

Abstract: Samples (0.13 ml), containing 0.02 to 1 ppm of H2O2, are injected into a carrier stream comprising 25 mM NaI - 0.5 mM ammonium molybdate - 0.2% of Na polystyrene sulfate. This is mixed with a reagent solution comprising 45 µM-4,4'-bis(dimethylamino)thiobenzophenone (I) - 1.3% of Triton X-100 - 13% of methoxyethanol - 0.05 M formate buffer (pH 3.5) in a reaction coil maintained at 30°C. The color change of I (thio-Michler ketone) is measured at 660 nm. Samples could be analyzed at a rate of 42 h-1. The calibration graph was rectilinear over the cited range. The system could be used to determine glucose indirectly, by incorporation of glucose oxidase. The calibration graph was rectilinear for 80 mg l-1. The method was used to determine glucose in urine. Samples (0.13 ml), containing 0.02 to 1 ppm of H2O2, are injected into a carrier stream comprising 25 mM NaI - 0.5 mM ammonium molybdate - 0.2% of Na polystyrene sulfate. This is mixed with a reagent solution comprising 45 µM 4,4'-bis(dimethylamino)thiobenzophenone (I) - 1.3% of Triton X-100 - 13% of methoxyethanol - 0.05 M formate buffer (pH 3.5) in a reaction coil maintained at 30°C. The color change of I (thio-Michler ketone) is measured at 660 nm. Samples could be analyzed at a rate of 42 h-1. The calibration graph was rectilinear over the cited range. The system could be used to determine glucose indirectly, by incorporation of glucose oxidase. The calibration graph was rectilinear for 80 mg l-1. The method was used to determine glucose in urine.
Hydrogen peroxide Glucose Urine Spectrophotometry Triton X Buffer pH Calibration Enzyme Surfactant

"Determination Of Residual Chlorine In Tap Water By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1988 Volume 208, Issue 1-2 Pages 317-320
Michio Zenki, Hirohisa Komatsubara and Kyoji Tôei

Abstract: The sample (170 µL) was injected into water carrier (0.8 mL min-1) and mixed with the reagent (3 mg of thio-Michler`s ketone in 30 mL of 2-methoxyethanol, 3 mL of Triton X-100, 100 mL of 0.14 M dodecylbenzenesulfonate and 100 mL of 0.1 M formate buffer at pH 3.5). Absorbance was measured at 640 nm, and the calibration graph was rectilinear from 0.2 to 1.0 mg L-1 of Cl. Other ions present in tap water did not interfere.
Chlorine, residual Water Spectrophotometry Interferences Surfactant Triton X