- Sunday, January 1, 2006
- Published at:J. Saudi Chem. Soci., 2006 Vol. 10, No.2 271-284
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The kinetics oxidation of L-cysteine by 3-di-2-pyridylketone-2-thiophenylhydrazone-iron(III) [Fe(DPKTH)2]
3+ complex in acidic medium was studied spectrophotometrically at 36C o temperature. The differential rate method (initial rate) was served in this investigation. The molar ratios of DPKTH to iron(III) and iron(II) individually, were found to be [2:1] [DPKTH : iron(III)/(II)]. The reaction was stroked to be first-order with respect to iron(III) and L-cysteine, second-order with respected to DPKTH ligand and reversed second-order with respected to hydrogen ion concentration. Added salts did not affect the rate and no free radical was detected when radical detector was placed in the reaction mixture. Ethanol solvent ratio was found to effect both the initial rate and the maximum absorbance (λmax) of [Fe(DPKTH)2]2+ complex. The initial rate rose when the temperature was increased which empowered the activation parameters calculations. From the evaluation of
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- Saturday, January 27, 2001
- Published at:Not Found
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Two spectrophotometric methods are described for the determination of tiopronin in pharmaceuticals. They are based on the oxidation-reduction reaction between tiopronin and iron (III), then forming a complex between iron (II) and ferrozine or di-2-pyridyl ketone-2-thiophenoylhydrazone. The produced colored iron (II)-ferrozine complex [system I] absorbs at 562 nm, while the iron (II)-di-2-pyridyl ketone-2-thiophenoylhydrazone complex [system II] absorbs at 656 nm. The effect of different factors such as: pH, reagent concentration, time of reaction, temperature and the tolerance amount of the common excipients have been studied. Applying the optimum
working conditions, tiopronin can be determined over the range 0.2-8.6 and 0.5-17.0 ppm and with molar absorptivities of 2.0x10
4 and 1.0x104 l mol-1cm-1 for systems I and II, respectively. Both methods offer high selectivity, sensitivity and accuracy with a relative standard deviation (RSD) of less than 1.1% for five measurements. Th
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- Monday, January 1, 2001
- Published at:Not Found
- ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 22125-ORGN 25-ORGN Part 2 2001
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- Monday, May 3, 1999
- Published at:TALANTA -OXFORD THEN AMSTERDAM- 0039-9140; 1999; VOL 50; NUMBER 4
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A method for spectrophotometric determination of nitrite and nitrate is described. This method is based on the reduction of phosphomolybdic acid to phosphomolybdenum blue complex by sodium sulfide. The obtained phosphomolybdenum blue complex is oxidized by the addition of nitrite and this causes a reduction in intensity of the blue color. The absolute decrease in the absorbance of the blue color or the rate of its decrease is found to be directly proportional to the amount of nitrite added. The absorbance of the phosphomolybdenum blue complex is monitored spectrophotometrically at 814 nm and related to the concentration of nitrite present. The effect of different factors such as acidity, stability of the complex, time, temperature, phosphate concentration, molybdenum concentration, sodium sulfide concentration and the tolerance amount of other ions have been reported. Maximum absorbance is at 814 nm. The range of linearity using the conventional method is 0.5–2.0 ppm with m
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- Tuesday, May 20, 1997
- Published at:Not Found
- An accurate fast spectrophotometric method for the determination of cysteine and N-acetylcysteineis presented, based on the oxidation of these amino acids by ferric ions in the presence of ferrozine,whereby a violet-coloured complex is formed which absorbs at 562 nm. The method was satisfactory for thedetermination of cysteine and N-acetylcysteine in samples within the range 0.02-6.00 ggm1-1. Effectsof time, acidity, ferric ions, ferrozine, sodium perchlorate concentrations and the tolerance limit for other amino acids have been reported. The method was applied to the determination of cysteine in amino acids mixtures and N-acetylcysteine in pharmaceutical preparations.
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RSS
Maher Abdel Razzak Abu-Eid Natsheh