Sequential-Injection Procedure for Determination of Iodide in Pharmaceutical and Drinking Water Samples by Catalytic Reaction with Spectrophotometric Detection

A novel sequential-injection system was developed for determination of iodide at very low concentrations by using a kinetic method. The method is based on the catalytic effect of iodide on the redox reaction between Ce4+ and As3+ first described by Sandell and Kolthoff. The calibration curve is constructed by measuring the decrease of Ce4+ absorbance versus iodide concentration with a delay time of 30 s. The detection limit is 1.5 μg/L, the working temperature is 45°C, and the working range is 0.002–0.5 mg/L. Reasonable agreement was obtained when the method was applied to pharmaceutical and drinking water samples. The method has a sample throughput of approximately 15/h.