Spectrophotometric determination of sulphite based on the catalytic oxidation of hydrogen sulphite

Abstract

A method based on the oxidation of hydrogen sulphite to hydrogen sulphate by dissolved oxygen with 1,2,3,4-thiatriazol-5-thiolate ion as catalyst has been developed for the determination of sulphite. The decrease in absorbance at 313 nm and the observed rate constant, k_obs, for the reaction were used as a measure of the sulphite (or hydrogen sulphite) concentration. The determination of sulphite (or hydrogen sulphite) can be carried out in the 1.0 × 10^–3–1.0 × 10^–4M(or 6.0 × 10^–4–6.0 × 10^–5M) concentration range with a standard deviation of 1.5 × 10^–5M(or 7.0 × 10^–6M) at pH 7 by using plots of ΔA, A_∞ and k_obsversus the sulphite or hydrogen sulphite concentration, respectively. The method described here is specific for S^IV compounds.