Kinetic-Spectrophotometric Determination of Iodide Based on its Inhibitory Effect on the Decolorization Reaction of Methyl Orange

Abstract

A simple, sensitive, rapid and reliable method has been developed for spectrophotometric determination of iodide based on its inhibition effect on the redox reaction between bromate and hydrochloric acid. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. The variables affecting the rate of the reaction were investigated. Under the optimum conditions, the limit of detection is 1.5 × 10-7 mol L-1 and calibration range is 2.0 × 10-6–1.3 × 10-4 mol L-1 of iodide. The linearity range of the calibration graph is depends on bromate concentration. The relative standard deviation of ten-replication determination of 8.2 × 10-5 mol L-1 iodide was 1.4%. The proposed method was applied to the determination of iodide in natural water samples with satisfactory results.