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
Website: @unf

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Citations 4

"Kinetic Study And Analytical Applications Of The Micellar Catalysed Reactions Of 1-fluoro-2,4-dinitrobenzene With Thiols Using A Fluoride-selective Electrode"
Analyst 1993 Volume 118, Issue 8 Pages 1001-1006
Athanasios M. Gerakis and Michael A. Koupparis

Abstract: The reaction between a thiol and 1-fluoro-2,4-dinitrobenzene (I) in the presence of a surfactant and NaF was studied kinetically by using an Orion model 96-09 fluoride electrode for potentiometric measurement in various buffered media. Optimum conditions for the determination of, e.g., mercaptoacetic acid, benzenethiol or thiosalicylic acid comprised 2 mM hexadecylpyridinium chloride, 0.01 M Tris buffer of pH 7.5, initial I concentration. 0.86 mM, temperature 25°C, and fixed-time measurement at 11 s. Rectilinear response was obtained for, e.g., 10^-250 or 5-75 µM-benzenethiol or -thiosalicylic acid, respectively. The method was used for the determination of mercaptoacetic acid in hair-waving and depilatory preparations. A manifold for flow injection potentiometric determination of thiols is also described.
Mercaptoacetic acid Benzenethiol Thiosalicylic acid Electrode Potentiometry Micelle Kinetic Optimization Buffer

"FIA - Extraction Applied To The Limit Test For Heavy Metals"
J. Pharm. Biomed. Anal. 1989 Volume 7, Issue 8 Pages 937-945
Lars-Göran Danielsson* and Zhao Huazhang

Abstract: Heavy metals in various samples were determined by flow injection extraction - spectrophotometry (e.g., at 274 nm) as their diethyldithiocarbamate complexes. Analytical parameters were chosen such that the sensitivities for toxic metals were enhanced compared with those for less toxic ones; e.g., at pH 3.5 in the presence of 3 mM EDTA the response to Fe, Mn, Ni and Zn was suppressed, but that to Pb was not. Calibration was effected with standard Pb solution, and the heavy metal content was calculated as Pb. The system was more sensitive than the standard procedure based on precipitation of colloidal sulfides. Relative responses for various ions at pH 3.5 and 4.7 in the presence and absence of EDTA are reported, as are results obtained on analytical-grade salts, pharmaceutical raw materials and household commodities. A method is presented that allows rapid determination of the total concentration of heavy metals in a sample. The method is based on FIA-extraction and photometric measurement of the metals as their dithiocarbamate complexes. The analytical parameters have been chosen such that the sensitivities for toxic elements are enhanced compared with those of less toxic heavy metals. The sampling capacity of the system is 40 samples h-1 and the repeatability (RSD) is 1.9% at 0.1 mg 1-1. Raw materials for the production of pharmaceuticals as well as analytical grade salts and household commodities have been tested.
Metals, heavy Lead Spectrophotometry Sample preparation Sensitivity Calibration Extraction Complexation

"Flow Injection Spectrophotometric And Amperometric Determinations Of Ammonia With Glutamate Dehydrogenase Reactor"
Bull. Chem. Soc. Eth. 1993 Volume 7, Issue 2 Pages 99-112
Ghirma Moges, Theodros Solomon, Gillis Johansson

Abstract: A flow injection method for indirect spectrophotometric and amperometric determinations of ammonia and ammonium, based on a 100 µL-glutamate dehydrogenase (GIDH) reactor, is described. GIDH was immobilized on controlled pore glass after silanization and glutaraldehyde activation. Injections of 50 µL standard ammonium chloride solutions to the carrier (water) produced peaks proportional to 3-1400 mM ammonia with a detection limit of 3 mM. The reagent stream delivered 0.2-0.6 mM NAD (NADH), 3.0 mM a-ketoglutarate and 4.0 mM adenosine-5'-diphosphate (ADP, activator) in 0.1 M Tris-acetate or phosphate buffer. Monitoring the decreasing NADH concentration after the enzymatic reaction produced peaks which formed the basis for measuring ammonia. Detection was made with a flow-through spectrophotometer (at 340 nm) or amperometric detector with a wall-jet phenoxazine-modified graphite electrode, held at 50 mV vs SCE (SCE). PH optima were 7.7-8.5 for the optical detector and 7.5-7.9 for the electrochemical detector. The system was applied to the determination of ammonium salt in commercial crude tryptophanase. The reactor was stable only for five days when used with Tris (pH 8.0-8.5) and stored in 0.1 M phosphate buffer (pH 7.0) at 4°C between uses but stability improved when potassium phosphate buffer (pH 7.8) was the reagent carrier and the storage buffer contained 10 mM ammonium chloride.
Ammonia Amperometry Spectrophotometry Enzyme Indirect Controlled pore glass

"Flow Injection Analysis. 2. Equipment And Analytical Applications"
Rev. Chim. 1990 Volume 41, Issue 7-8 Pages 623-628
Danet, A.F.;Luca, C.

Abstract: A review is presented, with 22 references, of the principles and applications of the cited technique for the analysis of food stuffs, agricultrual products, drugs, products of biotechnology and environmental pollutants.
Biotechnology Review