NON-IODIDE RADIOACTIVITY IN COMMERCIAL SOLUTIONS OF SODIUM RADIO-IODIDE (I131)1

Abstract

Some samples of commercially available solutions of sodium radio-iodide (I¹³¹) were found to contain radioactive iodine in a form electrophoretically and chromatographically different from iodide. This material (designated “S”) was anionic, was not affected by reducing agents in neutral or alkaline solution and its radioactivity could be converted almost completely to iodide by heating or by acidifying the solution. Errors in the estimation of thyroidal uptake of iodide could conceivably occur under certain circumstances if tracer solutions containing appreciable “S” were used. In the more recently available solutions of sodium radio-iodide (I¹³¹), some of which contained cysteine hydrochloride, only iodide-I¹³¹ has been detected.