The use of kinetic methods for the determination of ultra-trace amount of iodide in water

A new method for the determination of ultra-trace amounts of iodide ion w as developed. The proposed method employs ABTS, (2.2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid)), as the chromogenic reagent, and made full use of the advantages of stopped-flow methodology. This method was found to be selective and sensitive. The method was based on the monitoring of the alteration in the rate of formation of the cation radical of ABTS by oxidation with chloramine-T using a stopped-flow system. Traces of iodide markedly increases the rate of the reaction. The alteration is proportional to the concentration of the iodide which can be determined over the range 0–50 ppb with an RSD of less than 0.5% over this range.