SEPARATION OF URINARY THIOLS AS TRIBUTYLTINMERCAPTIDES AND DETERMINATION USING CAPILLARY ISOTACHOPHORESIS

The essential steps in the assay included electrolytic reduction of di sulphides, neutralization, extraction of thiols with 0.1 M tributyltin hydroxide in octane, stripping of the extract with 2% acetic acid, fi xing the washed-out amino thiols to a cation exchanger, elution with 2 M hydrochloric acid, oxidation with bromine and evaporation. The rema ining octane extract was decomposed by dodecanethiol, the mercapto aci ds were washed out, oxidized with bromine and evaporated. Both residue s were dissolved in water and analysed using capillary isotachophoresi s at pH 3.0. Cysteamine was extracted from reduced urine at ca. pH 10, decomposed by dodecanethiol and re-extracted to boric acid followed b y determination as a cation. The presence of the following thiols in u rine has been confirmed: mercaptoacetic acid, 3-mercaptolactic acid, 2 -mercaptopropionic acid, acetylcysteine, mercaptoethanol, cysteine, ho mocysteine and an un-identified amino thiol. Cysteamine and 3-mercapto propionic acid could not be detected. Captopril, homocysteine and cyst eine were determined quantitatively.