Spectrophotometric determination of bromate by the oxidation of Pyrogallol Red

Abstract

A method is proposed for the determination of bromate based on the oxidation of Pyrogallol Red (PGR) in a sulphuric acid medium. The kinetic data show that the initial reaction rate increases on increasing the sulphuric acid concentration. Under the optimum conditions of 2 mol dm^–3 H₂SO₄ and a time of 5 min bromate can be determined in the range 0–3.08 × 10^–5 mol dm^–3; the limit of detection is 7 × 10^–7 mol dm^–3 of BrO₃^– and the limit of quantitation is 2.3 × 10^–6 mol dm^–3 of BrO₃^–. The stoicheiometry is 3:2 (bromate to PGR). The reaction is second order with respect to H₂SO₄ concentration, first order with respect to bromate concentration and 0.5 order with respect to PGR concentration. The precision, accuracy and selectivity of the method are discussed.