Determination of total iodine in urine, stool, diets, and tissue.

13ETIiRMINATION of total iodine in various materials has become of increasing interest, especially in nutritional studies. Several methods are available for such determination. Many of them have been principally concerned with the protein-bound iodine fraction in serum (1, 2). Other methods for iodine determination have appeared from time to time. Mathews et al. (3) have proposed a method which requires large amounts of biologic specimens for good results. Widstr#{246}mand Bj#{246}rkman (4) have reported that losses of iodine by the dry-ash technic could be minimized by using potassium carbonate in place of sodium carbonate. Van Middlesworth (5) found that the Barker dry-ash method gave low recovery rates, in the range of 68-86%. Widstr#{246}mand Claeson (6) found that for the determination of total iodine in urine, a carrier medium such as zinc hydroxide was necessary to prevent losses of iodine with the dry-ash technic. Rodgers and Poole (7) advocated wet-ash digestion after which the iodine is distilled off by use of a special distillation apparatus. Barkley and Thompson (8) have reported an amperometric method for determination of total iodine in sea water; this method is not applicable directly to specimens of a biological nature. Since the method of Zak, as modified by two of us, has worked well for determination of protein-bound iodine and total iodine in serum (9), we decided to investigate its reliability for the determination of total iodine in urine, stool, diet, and tissue.