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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Hideji Tanaka

Abbrev:
Tanaka, H.
Other Names:
Address:
Faculty of Pharmaceutical Sciences, Tokushima University, Sho-machi, Tokushima 770-8505, Japan
Phone:
+81-88-633-7258
Fax:
+81-88-633-9508

Citations 7

"Determination Of Acid Dissociation Constants Based On Continuous Titration By Feedback-based Flow Ratiometry"
Talanta 2004 Volume 64, Issue 5 Pages 1169-1174
Hideji Tanaka,,, Takahiro Tachibana, Risa Oda and Purnendu K. Dasgupta

Abstract: We propose a method for the determination of acid dissociation constants based on the rapid detection of the equivalence point (EP) by feedback-based flow ratiometry and the subsequent estimation of the half equivalence point (EP1/2). The titrant (e.g., NaOH) flow rate FB was varied in response to a control voltage Vc from a controller, while the titrand (e.g., CH3COOH) flow rate FA was held constant. The pH of the mixed solution was monitored downstream from the confluence point of the solutions following a knotted tubular mixer. Initially, Vc was increased linearly. At the instance the detector sensed EP, the ramp direction of Vc changed downward. The pH increased further because of the lag time between the mixing of solutions and the sensing of pH. Following the pH maximum, the pH decreased. The EP was sensed again in this downward scan. The Vc that gives EP1/2 was computed from the Vc just at the time of the EP detection. The Vc was held constant at this level for 18 s, and the plateau pH value thus obtained was taken to be the pKa of the analyte subject to activity corrections. Studies on the dependence of the pKa on the ionic strength or dielectric constant of the solution were conducted in an automated fashion by delivering NaCl solution or acetonitrile through an additional channel. Satisfactory results were obtained with good throughput (53 s per determination) and precision (RSD[ap]0.3%) for various acids.

"Online Generation Methods For Highly Reactive Reagents And Their Application In Flow Analyses"
J. Flow Injection Anal. 1997 Volume 14, Issue 1 Pages 3-14
Tanaka, H.

Abstract: NA
Review

"Application Of Pretreatment Methods Using Electrolysis-generated Redox Reagents For Flow Analysis"
Bunseki Kagaku 1998 Volume 47, Issue 2 Pages 79-91
Hideji TANAKA

Abstract: Reagents having a high redox power (cobalt(III) and chromium(II) ions) were applied to online pretreatment in flow analyzes. A flow-through electrolysis cell for continuous reagent generation was assembled and put in a system of FIA or HPLC. The cobalt(III) ion was strong enough to oxidatively decompose diverse organic compounds within a short time (<10 min, depending on the chemical structure of the compounds), even at ordinary temperature Thus, the cobalt(III) pretreatment was successfully applied to the FIA determination fo total mercury and organic phosphorus; organomercury and organic phosphorus compounds were digested to mercury(II) and phosphate ions, respectively, which are detectable species by subsequent cold-vapor (CV)-at. fluorescence (AF) and Molybdenum Blue spectrophotometric detections. Further, the author has proposed a novel method for a chemical oxygen-demand determination based on cobalt(III) oxidation, because it can be done rapidly using a simple FIA manifold with no requirement for a heating process. Chromium(II) ion, on the other hand, has a very strong reducing power. This ion can completely reduce the stable mercury-iodide complex, HgI42-, to elemental mercury, thus enabling AF detection. In the present method, the addition of iodide ion (>10 mg L-1) to a sample solution gave good results with respect to the accuracy and precision, because iodide ions act as a stabilizer against the coexisting interfering substances and/or mercury deposition at the inner wall of the manifolds. A reversed-phase HPLC system coupled with CV generation based on chromium(II) reduction and AF detection was developed for organomercury speciation. An online reagent-generation method was concluded to afford great advantages to flow analyzes. It enables the application of highly reactive (thus unstable) for poisonous reagents, which are impracticable under normal anal. condition, because the process from reagent generation to its use can be done within a short time in semi-closed flow system isolated from the atmosphere.
Mercury Organophosphorus compounds Chemical oxygen demand Spectrophotometry Spectrophotometry HPLC Electrochemical reagent generation Interferences Redox

"Cobalt(III) Oxidation Of Organic-compounds And Its Application To A Determination Of Chemical Oxygen-demand At Room-temperature"
Anal. Sci. 1997 Volume 13, Issue 4 Pages 607-612
H. TANAKA, H. MORITA, S. SHIMOMURA and K. OKAMOTO

Abstract: Cobalt(III) oxidation of diverse organic compounds was studied in a batch system. An aqueous solution of an organic compound was mixed with a cobalt(III) solution (ca. 0.04 mol L-1), prepared through the electrolysis of a cobalt(II) solution in a strong acidic medium, with a volume ratio of 1:2. The oxidation of the organic compound was evaluated from the decrement in absorbance of the mixed solution at 610 nm, the wavelength of absorption maximum of the cobalt(III) ions. The cobalt(III) ions were found to be strong enough to oxidatively decompose organic compounds at room temperature; the oxidation was rapid and almost complete in 10 min. The chemical oxygen demand (COD) of sample solutions was calculated from the amount of cobalt(III) ions consumed for the oxidation. The obtained COD value for each sample was comparable to that determined by an official method based on permanganate oxidation. It is concluded that not only is the cobalt(III) oxidation practical for the treatment of organic compounds but it has possibilities as a novel method of COD determination, because it can be done rapidly in a simple operation with no requirement for heating. 29 References
Chemical oxygen demand Water Spectrophotometry Indirect Method comparison Standard method

"Flow Injection Analysis With Online Preconcentration Of Trace Selenium"
Anal. Sci. 1991 Volume 7, Issue 4 Pages 617-621
E. AOYAMA, K. AKAMATSU, T. NAKAGAWA and H. TANAKA

Abstract: The cited system (details given) was developed for determining very low concentration. of Se(IV). The Se was selectively collected as selenotrisulfide on a micro-column (5 cm x 1 mm) packed with resin loaded with Bismuthiol-II sulfonate and eluted with aqueous penicillamine solution The resulting penicillamine selenotrisulfide was introduced into the flow injection analyzer. (details given); detection was at 565 nm. Interference from Cu ion was eliminated by adsorption of Cu on the resin as bathocuproine disulfonate chelate. Determination of Se in a standard biological sample, e.g., lobster was used to confirm the reliability of the method.
Selenium Biological Spectrophotometry Column Interferences Preconcentration Resin Solid phase reagent

"Determination Of Selenium By Flow-injection Analysis Based On The Selenium(IV)-catalyzed Reduction Of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium Bromide"
Anal. Sci. 1991 Volume 7, Issue 1 Pages 103-107
E. AOYAMA, N. KOBAYASHI, M. SHIBATA, T. NAKAGAWA and H. TANAKA

Abstract: Sample solution was mixed with NaOH (to pH 7) and 0.1 M phosphate buffer solution (pH 7) containing 12 mM bathocuproine disulfate and the mixture was injected into a carrier solution of 0.1 M phosphate buffer solution (0.2 mL min-1) and through a column (5 cm x 4.6 mm) of Chemcasorb 3-ODS-H operated at 40°C. The eluate was mixed with 7.3 mM dithiothreitol and 3-[4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and the absorbance of the solution was measured at 565 nm. Analysis time was 8 min. The calibration graph was rectilinear for 1.3 pmol to 1.2 nmol Se (IV) and the coefficient of variation was 2.2%. The method was applied in the analysis of lobster refrence material, recovery was 103% for 5 µg mL-1 of Se and no interference was present.
Selenium NRCC TORT-1 Spectrophotometry Buffer Catalysis Column Heated reaction Interferences Solid phase reagent

"Determination Of Dissociation Constants Of Weak Acids By Feedback-based Flow Ratiometry"
Anal. Chim. Acta 2003 Volume 499, Issue 1-2 Pages 199-204
Hideji Tanaka, Kiriko Aritsuka, Takahiro Tachibana, Hiroshi Chuman and Purnendu K. Dasgupta

Abstract: We applied the principle of feedback-based flow ratiometry, originally developed for continuous titrations, to the determination of acid dissociation constants (Ka). The titrant (NaOH) flow rate FB was varied in response to a control voltage Vc from a controller, while the total (titrant+titrand) flow rate FT was held constant. The titrand was aspirated to the flow system at the flow rate of FT-FB, and mixed with the titrant at the confluence point. Downstream, the pH of the mixed solution was measured with a glass electrode. Initially, Vc (thus FB) was ramped upward linearly. At the instant the detector sensed the half equivalence point, Eq1/2, where the buffer capacity is maximum, the algorithm reversed the ramp direction of Vc downwards. When Eq1/2 was sensed again, the algorithm reversed the ramp direction of Vc again, upwards. By repeating these processes automatically, time utilization efficiency of the procedure was improved by scanning Vc only in the range of interest. When the Vc scan range was thus constrained, the pH values corresponding to either a maximum or minimum in Vc, were equal to the pKa of the analyte. The pKa values thus obtained for various n-alkyl carboxylic acids and phosphoric acid agreed well with the literature. High throughput (ca. 26 s per determination) was attainable with reasonable precision (RSD<3%).