Determination of iodine in biological materials by neutron activation analysis

A method of determination of iodine (total and PBI) in serum, urine and other biological materials has been developed. The method consists in a gamma-spectrometric measurement of¹²⁸I activity after its radiochemical separation. The radiochemical separation procedure includes wet decomposition of the samples in a nitric acid medium followed by a few separation steps, the essential step being the substoichiometric extraction of iodide with a chloroform solution of tetraphenylarsonium chloride. Owing to the application of the substoichiometric separation, a high radiochemical purity of the separated iodine is achieved and the determination of the yield of radiochemical separation is not necessary.