Sub-stoichiometric isotope dilution analysis method for the determination of iodine in common salts using iodine-131 tracer

Abstract

A sub-stoichiometric isotope dilution analysis (SIDA) method was developed for the determination of iodine in different brands of common salts. An aqueous salt solution containing ¹³¹I tracer and NaI as carrier is oxidized by tartaric acid and KIO₃ and the liberated iodine is extracted with CCl₄. To the extract an aqueous solution of AgNO₃ is added in substoichiometric amount to obtain a colloidal solution of AgI. On adding sodium thiosulfate solution, the NaI so formed passes into aqueous solution, which is then counted. Several different brands of salt were analysed. The method is especially suitable for the determination of microgram amounts of iodide in the presence of excess of chloride.