NONSUPPRESSED ION CHROMATOGRAPHY OF CYSTE IN, PENICILLAMINE, AMINOETHANETHIOL AND DITHIOTHREITOL USING THE REDOX REACTION WITH TETRATHIONATE ION

A method for the determination of cysteine(CySH), penicillamine(PSH), aminoethanethiol (ASH) and dithiothreitol(DSH) was developed using non suppressed ion chromatography(IC) with UV detection (220 nm). Thiol co mpounds are converted to thiosulfate ion by the reaction with tetrathi onate ion and the thiosulfate ion produced in reaction solution is qua ntitatively determined by nonsuppressed IC with 4 mM phosphate buffer (pH 7.5) as the eluent. Sample solution for IC was prepared by adding two equivalents of potassium tetrathionate to the respective thiol com pound, and letting it stand for about 10 min, at 25-degrees-C for CySH and ASH, 50-degrees-C for PSH and 55-degrees-C for DSH. The calibrati on curves for thiol compounds were linear in the concentration range o f 2-100 muM. A relative standard deviation(%) of less than 1.5% was ob tained at concentrations of 10 approximately 100 muM thiol compounds. The detection limit for thiol compounds was 0.7 approximately 1 muM. A 100-fold molar excess of amino acid and cystine, and an equimolar exc ess of penicillamine disulfide did not interfere.