Fluorimetric determination of some thiol compounds in their dosage forms

A simple fluorimetric procedure was adopted for determination of three pharmaceutical compounds containing thiol groups namely, captopril, d-penicillamine and N-acetylcysteine. In this method, the drugs are treated with 1,2-naphthoquinone-4-sulfonic acid. The latter is reduced to 1,2-dihydroxynaphthalene-4-sulfonic acid which has a maximum fluorescence intensity at 480/318 nm ( λEm/Ex). The method is sensitive to 0.5–4.5 μg ml −1 with minimum detectability 0.05 μg ml −1 ( S/ N=2), and has been applied to determine these three thiols in their dosage forms. The results obtained are compared favourably with those obtained by their pharmacopeial methods.