Polarography of β-mercapto-ethylamine hydrochloride and its disulphide dimer

Abstract

A polarographic study of β-mercapto-ethylamine hydrochloride (MSH) and its disulphide has been made in Britton-Robinson buffer, perchloric acid, acetate-, phosphate-, ammonia buffer and NaOH medium, at pH values ranging from 2 to 12, at ionic strength 0·30 M and temperature 30° ± 0·2°C. At lower pH values, a normal anodic wave was observed. At pH values of alkaline range, a mixed anodic-cathodic wave was recorded. The cathodic wave at high pH values was taken to be due to possible oxidation of the thiol during the manipulation period. The waves for MSH showed a reversible nature at all pH values studied, pK for the (-SH) group of MSH being 10·0 4. The reduction is supposed to take place via mercury salt formation, and an equation for the electrode reaction at the dropping mercury electrode (dme) has been proposed. Polarograms of the disulphide of mercapto compound namely, ββ′-diaminoethyldisulphide dihydrochloride (MSSM) gave well defined, characteristically drawn-out, cathodic waves at all pH values studied. MSSM appears to undergo reduction in a quasi-reversible manner, involving two electrons. The reversible half-wave potentials ( E 1/2 r ) has been calculated from Matsuda and Ayabe equation for quasi-reversible cathodic waves.