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
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Turkish Journal of Chemistry

  • Publisher:
  • FAD Code: TJCH
  • CODEN: TJCHE3
  • ISSN: 1300-0527
  • Abbreviation: Turk. J. Chem.
  • DOI Prefix: 10.3906/kim-
  • Language: English
  • Comments: Fulltext from 1996 V20

Citations 6

"Voltammetric And Flow Injection Amperometric Determination Of Cysteine At A Glassy Carbon Electrode In The Presence Of Copper(II) Ions"
Turk. J. Chem. 2003 Volume 27, Issue 4 Pages 513-519
ZEKERYA DURSUN, İLYAS ŞAHBAZ, F. NİL ERTAŞ, GÜREL NİŞLİ

Abstract: The voltammetric behavior of cysteine was investigated in the presence of Cu(II) ions at a rotating glassy carbon electrode (RGCE). Two reduction peaks related to the successive reduction of the cysteine complexes of Cu(II) and Cu(I) ions were observed at -0.30 and -0.60 V vs. SCE respectively. These peaks were increased upon the addition of cysteine into a pH 9.20 borate buffer solution containing 0.1 M KNO3 and 1.0 x 10^-5 M Cu(II) ions. The calibration curve was linear in the concentration range of 5.0 x 10^-10 -2.0 x 10^-8 M for cysteine by utilising the peak current at -0.6 V vs. SCE. In the flow technique, 50 µL portions of off-line prepared mixtures of 1.0 x 10^-5 M Cu(II) and varying concentrations of cysteine were injected into the carrier solution of pH 9.20 borate buffer containing 0.1 M KNO3 flowing through 25 cm transmission tubing (i.d. 0.75 mm) at a rate of 1.5 mL/min. The signals were monitored at -0.60 V vs. SCE. The calibration graph was found to be linear in the concentration range 1.0 x 10^-9 -1.0 ? 10 -7 M with a relative standard deviation of 1.0% (n = 5) for 5.0 x 10^-8 M cysteine. The detection limit was calculated as 5 x 10^-10 M for S/N = 3 ratio.

"Flow Injection Speciation Analysis Of Manganese In Real Samples By Diphenylcarbazide-spectrophotometric Determination"
Turk. J. Chem. 2003 Volume 27, Issue 2 Pages 227-233
KAZEM KARGOSHA, MEISSAM NOROOZIFAR

Abstract: The flow injection speciation of manganese in aqueous solution using a spectrophotometry method of detection is presented. Manganese (VII) can be determined spectrophotometrically at 308 nm after the reaction with Sym-diphenycarbazide in buffered at pH = 3.05 with phosphate. Under the optimized conditions, total manganese concentration can also be determined after oxidation of Mn2+ to MnO-4 and then Mn2+ concentration can be calculated from the difference. The linear range of determination is 0.047-4.50 mg/l with a 3? detection limit of 31 ?g/l. The proposed method is applied to the determination of MnO-4 and Mn2+ in effluent streams and foods with a relative standard deviation better than 1.85%. A sampling frequency of up to 24 h-1 can be achieved. Interfering ions can be removed by an ion-exchange column built into the flow injection system.

"Flow Injection Amperometric Determination Of Ascorbic Acid Using A Photoelectrochemical Reaction After Immobilization Of Methylene Blue On Muscovite"
Turk. J. Chem. 2003 Volume 27, Issue 2 Pages 167-180
YUSUF DİLGİN, ZEKERYA DURSUN, GÜREL NİŞLİ

Abstract: The photoelectrochemical determination of ascorbic acid (AA) was studied based on the photochemical reduction of methylene blue (MB) in 0.1 M phosphate buffer (pH 7.0). MB was used as a redox mediator for the modification of a carbon paste electrode (CPE) due to its facile reducible-oxidizible behaviour. Muscovite, which has a layered structure, was found to be a good and stable supporting material for the immobilization of MB by an ion exchange reaction. The dye is strongly retained and not easily leached from the matrix. MB was reduced to nearly quasi-reversible at the modified carbon paste electrode (MCPE). The oxidation peak potential of leuco-methylene blue (LMB) shifted from -100 mV to 50 mV in the presence of AA. For photoelectrochemical amperometric studies, the operational potential was kept constant at + 50 mV according to the oxidation of LMB, which was produced from the chemical reaction between AA and MB on the modified electrode surface. A laboratory-built flow cell system was constructed for the direct irradiation of the electrode surface with a 500-W halogen lamp. The optimum conditions for the flow injection (FI) amperometric determination of AA were 1.5 mL/min flow rate, 50 µL sample loop and 50 cm transmission tubing length and at a frequency of 60 samples per hour. AA could be determined in the concentration range 1.0 x 10^-6-1.0 x 10^-4 M by using a photoelectrochemical FI method. The detection limit of this method was 1.0 x 10^-8 M. The relative standard deviation of five replicate injections of 6.0 x 10^-5 M AA was 2.0% in photoelectrochemical FI. The results obtained by the proposed procedure are in good agreement with those established using the triiodide procedure for the AA determination of pharmaceutical products.

"Flow Injection Extraction - Spectrophotometric Determination Of Bismuth With Di-(hydrogenated Tallow Alkyl) Dimethylammonium Chloride"
Turk. J. Chem. 2002 Volume 26, Issue 3 Pages 345-349
SA BARAKAT

Abstract: Bismuth(III) (0-25 ?g/ml) is determined spectrophotometricaly at 513 nm after extraction into dichloromethane of the ion associate di-(hydrogenatedtallowalkyl)dimethylammonium tetraiodobismuthate. The reagent stream is distilled water, merged with 1.0 M sulfuric acid, 5% potassium iodide and 5% (w/v) ascorbic acid solution. The reagent stream is 0.2% (w/v) di-(hydrogenatedtallowalkyl)dimethylammonium chloride solution. The injection rate is 15 h-1. The calibration graph is linear up to 25 ?g/ml. The detection limit is 0.35 ?g/ml Bi. The system is applied on water samples and copper-based alloys.

"Flow Injection Analysis For Boron Determination By Using Methyl Borate Generation And Flame Atomic Emission Spectrometry"
Turk. J. Chem. 2001 Volume 25, Issue 3 Pages 305-310
DENİZ YURTSEVER SARICA, NUSRET ERTAŞ

Abstract: Boron is one of the least sensitive elements in atomic emission spectrometry. As various refractory substances interfere in the analysis and because of the low sensitivity, sample enrichment and the separation of the interfering matrix is needed. Methyl borate has many advantages because of its simple generation conditions and its stability in the absence of moisture. New procedures for the generation of methyl borate without using external heating have also been investigated to produce a more rapid determination of boron. The on-line combination of flow injection analysis using methyl borate generation with flame atomic emission spectrometry as the detector is proposed to provide sufficient enrichment factors in order to determine boron in different matrices. In order to obtain as much moisture-free medium as possible, all standard solutions were prepared in 60% H2SO4 (v/v) according to the experimental results. The effect of Ar flow rate, peristaltic pump rate, size of the tubings used, and length of the mixing coil to the emission signal were all studied. Furthermore, the design of the gas liquid separator, and several ways to transfer the signal to AES were also examined in detail. A linear calibration graph was obtained between 10 and 2000 ?g/mL with the equation y = 0.1105X - 1.496. The detection limit of the method was calculated as (3S) 2.96 ?g/mL or 0.74 ?g B.

"HPLC/hydride Generation AAS Coupling For The Speciation Of Sb(III) And Sb(V) In Wastewaters"
Turk. J. Chem. 2000 Volume 24, Issue 4 Pages 371-376
Nuray ŞatiroĞlu, Sema BektaŞ, Ömer GENÇ, Haydar Hazel

Abstract: A comparative study was made with two HPLC columns of different lengths (PRP-X 100, 250 mm x 4.1 mm id and PRP-X 100, 100 mm x 4.1 mm id) coupled to HGAAS for the speciation of inorganic SL(III) and Sb(V) species. The effects of eluent concentration and pH on the retention times of Sb species in Loth columns were investigated. The separation of Sb species was realized by using 50 mmol/L citrate solution at pH 4.0 as the eluent. The retention times were 2.0 min and 10.0 min in the 250 mm column, and 1.4 min and 3.6 min in the 100 mm column for Sb(V) and Sb(III) respectively. The hydrides were produced by adding 1% NaBH5 and 5.0 mol/L HCl solutions. The absorbance was linearly related to the Sb(V) concentration in the range 2.0-100 µg/L and to the Sb(III) concentration in the range 4.0-100 µg/L The detection limits obtained for Sb(V) and Sb(III) were 1.0 and 0.8 µg/L respectively. Since certified standards for antimony in aqueous solutions are not currently available, the accuracy of the method was checked by the analysis of both species in several spiked water samples. The optimized experimental conditions were applied for the speciation and determination of the species in mining industry wastewaters.