Ellman's reagent: interference in mercapto group determination, with special reference to cigarette smoke

Abstract

Cyanide, hydrogen sulphite and sulphide interfere in the determination of mercapto groups with Ellman's reagent [5,5′-dithiobis-(2-nitrobenzoic acid)] by nucleophilic substitution of the reagent. Such reactions produce significant analytical errors under certain conditions. Some saturated and unsaturated aliphatic aldehydes also interfere in the determination by formation of less reactive addition products with the mercapto compounds. When both types of compounds are present concurrently, as in cigarette smoke and related products, the aldehydes and the thionucleophilic reagents may react with each other and with other smoke components in a series of complex reactions. The degree of de-activation of mercapto groups by cigarette smoke and related products can be determined with Ellman's reagent only under carefully controlled conditions.