A method for the measurement of radioiodine in biological materials.

For the purpose of biochemical studies utilizing radioiodine 1131 as a tracer material, it is desirable to have a simple, sensitive, and thoroughly validated method for the measurement of the radioactivity of the biological samples. The present investigation was undertaken to provide such a method, with part,icular reference to the thyroid of the rat, but is adaptable with appropriate modifications to any biological material or compound. In this procedure t,he iodide in the sample is oxidized to iodate by a modification of t’he permanganate acid method of Riggs and Man (l), reduced to iodide, and the iodide precipit,ated as palladium iodide after the addition of a controlled amount, of carrier iodide. By this means there is obtained a controlled weight of 1131-containing precipitate which is independent of variations in the chemical composition and the amount of the original sample, and which may be easily filtered off for radioactivity measurement.