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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Kazuhisa Yoshimura

Abbrev:
Yoshimura, K.
Other Names:
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Department of Chemistry and Physics of Condensed Matter, Graduate School of Sciences, Kyushu University, Ropponmatsu, Fukuoka 810-8560, Japan
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Citations 6

"Equilibrium And Kinetic Studies On The Complexation Of Boric Acid With Chromotropic Acid"
J. Chem. Soc. Dalton Trans. 2000 Volume 2000, Issue 18 Pages 3136-3142
Chaoying Shao, Shiro Matsuoka, Yoshinobu Miyazaki, Kazuhisa Yoshimura, Toshishige M. Suzuki, D. A. Pacheco Tanaka

Abstract: The complexation of boric acid with chromotropic acid in aqueous solution was examined thoroughly by B-11 NMR measurements. Two peaks with chemical shift values of delta -17.7 and -18.0 were observed besides the free boric acid/borate peak and ascribed to the 1:1 and the 1:2 complexes, respectively. The 1:2 complex is formed in acidic solution, while the 1:1 complex prevails in a higher pH range. The formation constants for these complexes were evaluated based on the signal intensities of B-11 NMR spectra to be log beta(1)=-1.57 and log beta(2)=2.35, which are well consistent with those reported previously as well as that (beta(2)) obtained kinetically in this work. The chromatographic separation of the 1:2 complex from the other species enabled a kinetic study of the reaction which revealed that the reaction for 1:1 complex formation takes place much faster than that for 1:2 complex formation. The pH dependences of the rate constants of the forward and backward reactions of the 1:2 complexation could be interpreted by the catalytic role of hydrogen ions in the reactions. Plausible mechanisms for both the reactions of 1:2 complex formation and decomposition were proposed. On the basis of the equilibrium and kinetic information on the complexation, the optimum conditions for practical applications of the ligand so far reported could be well understood.

"Online Concentration And Flow Analysis Of Trace Amounts Of Bismuth With Anion-exchange Method And Ion-exchanger Absorptiometry"
Bunseki Kagaku 1987 Volume 36, Issue 11 Pages 656-661
Yoshimura, K.

Abstract: Bismuth (0.012 to 0.5 nmol) in various samples (e.g., 1 l of water) was pre-concentrated as a chloro-complex from 0.1 to 0.6 M Cl- by using a Dowex 1-X8 anion-exchange column (Cl- form; 100 to 200 mesh). Bismuth was desorbed with 0.15 M H2SO4 at a flow rate of 1.2 mL min-1 and mixed with a solution containing 1 M KI at 0.3 mL min-1. After introduction into the flow-through cell, the light path portion of which was filled with QAE Sephadex A-25 anion exchanger, the light attenuation due to the iodo-complexes of Bi (concentrated on the anion exchanger in the cell) was measured directly at 472 nm, with high precision. The calibration graph for Bi was rectilinear and the method was applied to samples of rocks and metals.
Bismuth Metal Geological Water Ion exchange Spectrophotometry Preconcentration Dowex Resin Sephadex Solid phase detection

"Implementation Of Ion-exchange Absorptiometric Detection In Flow Analysis Systems"
Anal. Chem. 1987 Volume 59, Issue 24 Pages 2922-2924
Kazuhisa Yoshimura

Abstract: Ion-exchange resin (Bio-Rad AG 50W-X12) was loaded as a 3 to 5-mm 'column' in a flow-through cell (1.5 mm i.d.) positioned in a spectrophotometer such that the light beam was incident vertically on the top of the resin column. Samples in dilute salt or acid solution containing 0.01 to 0.5 µmol of Cu(II) were introduced into the carrier stream of 14 mM HNO3 and the absorbance was monitored at 800 nm. Response was rectilinear over the range examined and at flow rates of 0.38 to 2.5 mL min-1. Copper ions were desorbed from the resin with 2 M HNO3. Small amounts of cations which absorb at 800 nm cause positive errors in the measurement.
Copper(II) Spectrophotometry Interferences

"Flow Analysis For Trace Amounts Of Copper By Ion-exchanger Phase Absorptiometry With 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline Disulfonate And Its Application To The Study Of Karst Groundwater Storm Runoff"
Anal. Chim. Acta 1992 Volume 268, Issue 2 Pages 225-233
Kazuhisa Yoshimura* and Shiro Matsuoka, Youji Inokura, Ushio Hase

Abstract: Water (8.3 mL; containing 0.8 to 80 ng of copper) was introduced into a carrier stream of aqueous 1% (v/v) HCl. Simultaneously, into a second carrier stream comprising 50 g of hydroxylammonium chloride and 200 g of citric acid in 500 mL of water mixed with 10 mL of 4% BL-9EX and adjusted to pH 6 with aqueous NH3 was introduced 2.1 mL of a solution of the cited reagent (50 µg mL-1 in the second carrier stream). The two carrier streams merged and aqueous 10% (v/v) HNO3 was introduced as desorbing agent before passage of the solution through a mixing coil and a flow-through absorptiometric detector containing QAE Sephadex A-25 to concentrate the Cu complex for continuous measurement of absorbance at 484 nm. The system afforded a detection limit of 0.08 ng mL-1 of Cu and selectivity was good. The method was used to monitor the infiltration of storm water from the soil into the underground river of a karst groundwater system. It could also be used to determine Cu in rock samples after microwave digestion with HNO3 and HF. Ion-exchanger phase absorptiometry was applied to flow anal. for trace amounts of Cu in water. The increase in the absorbance of the colored complex with 4,7-diphenyl-2,9-dimethyl-1,10-phenanthroline disulfonate, which was concentrated online on to an ion exchanger packed in a flow-through cell, can be measured continuously with a spectrophotometer at 484 nm. The detection limit was 0.08 ng/mL of sample solution. The proposed method permitted a highly sensitive, selective determination of copper in karst groundwater samples without any pre-concentration. By measuring the Cu concentration. response in water after a storm, the infiltration rate of rain water from the soil zone to the underground river of a karst groundwater system was estimated ~10-20 m/day.
Copper Ground Geological Rain Sample preparation Spectrophotometry Solid phase detection Sephadex

"Anion Exchanger As A Reaction/separation Medium - Absorptiometric Determination Of Trace Amounts Of Boron In Waters By On-line Complexation With Chromotropic Acid Presorbed On The Anion-exchange Column"
Analyst 2002 Volume 127, Issue 12 Pages 1614-1620
Chaoying Shao, Shiro Matsuoka, Yoshinobu Miyazaki and Kazuhisa Yoshimura

Abstract: A novel method of on-line absorptiometric determination for trace amounts of boron was developed based on the complexation with chromotropic acid presorbed on an anion-exchange column. On-line reaction and separation were achieved by controlling pH conditions in solutions to accelerate the 1:2 complex formation in the concentration process at pH 3 and to stabilize the complex in the separation process at pH 8. About 75% of the boron introduced into the stream was kinetically collected as the 1:2 complex on the column under the experimental conditions. The 1:2 complex was satisfactorily separated from excess reagent and matrix components by changing the concentration of NaClO4 in the eluent and its peak height on the chromatogram monitored at 350 nm was used for calibration. The sensitivity could be enhanced by increasing the sample amount introduced and the detection limits (3s) were 162 ng L-1 and 45 ng L-1 of boron, when 5.0 mL and 13.4 mL of the samples were used, respectively. The method has been successfully applied to the determination of boron in samples of river water, tap water and ion-exchanged water.
Preconcentration

"Application Of Ion-exchanger Phase Absorptiometry To Flow Analysis. Determination Of Trace Amounts Of Chromium(IV) In Water"
Analyst 1988 Volume 113, Issue 3 Pages 471-474
Kazuhisa Yoshimura

Abstract: Ion-exchanger phase absorptiometry was applied to the determination of trace amounts of chromium(VI) in natural waters using flow analysis. The product of the reaction of chromium(VI) with 1,5-diphenylcarbazide was introduced into a carrier solution stream in the flow system. The increase in absorption by the colored complex sorbed on a cation exchanger, with which the light-path of a flow-through cell had been partly filled, could be measured directly with high precision. When 4.4 mL of sample solution were pumped through, the sensitivity obtained was 160 times higher than that of the corresponding solution method. The detection limit was as low as 0.5 ng of chromium(VI). Cations such as calcium and background electrolytes present in natural waters at high concentrations caused a change in the background attenuation. For fresh water, this effect could be removed only by passing the sample solution through a small hydrogen-form cation-exchange column. For sea water, it is necessary to use a calibration graph prepared at similar concentrations to those in the sample solution. Without pre-concentration, the proposed method is directly applicable to the analysis of natural water samples containing chromium(VI) at less than 1 µg dm-3.
Chromium(VI) Sea Ion exchange Spectrophotometry Preconcentration