Two Simple Methods for Measuring Iodine in Urine

Urinary iodine excretion is currently the most convenient laboratory marker of iodine deficiency. Accelerating international interest in correcting this condition demands rapid, simple methods for assessment and monitoring. We describe two adaptations of the Sandell-Kolthoff reaction, in which urine is first digested with chloric acid and iodine then determined from its catalytic reduction of ceric ammonium sulfate in the presence of arsenious acid. Both methods use gentle digestion by chloric acid in a heating block. Method A detects iodine in a colorimeter, method B by the indicator ferroin and a stopwatch. Results with 12 samples ranging from 1.8 to 19.0 μg/dL (0.14-1.48 μmol/L) differed from those in a reference laboratory by a mean of 9.1% for method A and 15.7% for method B. One technician can perform at least 150 tests per day at a total cost of less than $0.50 each. The speed, low cost, and simple instrumentation make these methods well suited to epidemiological assessment of iodine deficiency in developing countries.