Measurement of iodine concentration in biological material.

Determination of iodine in biological material presents technical problems because of the large amounts of organic material present and because the concentration of iodine is often low. Many workers have used a chloric acid-digestion procedure (1), but this is tedious, and Richmond (2) found it less satisfactory for accurate measurement of fecal iodine than for determining iodine in serum or urine. Significant errors may arise from underor overdigestion. Combustion of feces is a more convenient way of liberating iodine from organic material, and seems to be a satisfactory method for accurately determining iodine both in feces and in foodstuffs (3-5). Sodium hydroxide may be used to recover the liberated iodine (5, 6). Introduction of the Model 300 Tri-Carb Sample Oxidizer (Packard Instruments Co., Downer’s Grove, Ill. 60515), designed for the preparation of samples containing tritium for liquid scintillation counting, which made use of a new automated combustion procedure (7) led us to investigate whether this equipment could conveniently be used to prepare biological samples for iodine estimation. Methods