Kinetic Catalytic-Spectrophotometric Determination of Trace Amount of Iodide

Abstract

A new, simple, sensitive and selective catalytic spectrophotometric method was developed for the determination of ultra trace amounts of iodide. The method is based on the catalytic effect of iodide on the oxidation of Indigo carmin by iodate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Indigo carmin at 612 nm with a fixed-time method. The decrease in the absorbance of Indigo carmin is proportional to the concentration of iodide in concentration range 40.0-200.0 ng/ mL, with a fixed time of 0.5-2.5 min from initiation of the reaction. The limit of detection is 34 ng/mL iodide.The relative standard deviation of 0.060 and 0.10 μg/mL iodide was 1.8 and 2.2 %, respectively. The method was applied to the determination of iodide in water.