Differential Determination of Iodate and Iodide by a Kinetic-Catalytic Method

Abstract

An analytical method for the determination of iodate and iodide ions at theμg l^-1 level in mixtures was investigated. Iodide in samples was first oxidized with sodium nitrite; the free iodine liberated was then released from the solution by heating. Excess nitrite was destroyed with amidosulfuric acid (sulfamic acid). The iodate remaining in the solution was determined by a kinetic-photometric method based on the catalytic effect of iodine on the oxidation of chlorpromazine by hydrogen peroxide in a sulfuric acid solution. The total iodine was also determined by a similar analytical procedure without carrying out operations for the removal of iodide; the iodide was found from the difference between the two results. Mixtures of iodate and iodide in the 0.2-5μg l^-1 range of total iodine could be determined within an error of 10%. The proposed method has been successfully applied to a differential determination of iodate and iodide in natural fresh-water samples.