AUTOMATED MEASUREMENT OF URINARY IODINE WITH USE OF ULTRAVIOLET-IRRADIATION

We have modified an automated measurement system of urinary iodine (UI ) and established a sensitive UI assay system by using ultraviolet (UV ) digestion. The automated system is sensitive enough to detect concen trations of UI <0.78 mu mol/L (<10 mu g/dL) in a small volume of urine (500 mu L). Sample throughput is >30/h, including a water washing. Th e within-assay imprecision (CV) was less than or equal to 10% in the U I range of 0.10-3.00 mu mol/L; the between assay CV was usually less t han or equal to 15% in the same range. Analytical recovery of iodine a dded to urine samples was consistently >90%. The theoretical values we re recovered when UV irradiation was used but not in its absence. High (supraphysiological) doses of thiocyanate or ascorbic acid, which are major interfering substances to the ceric-arsenious acid reaction, di d not interfere with this system. The correlation between UI determine d by this method and by the acid digestion method was linear (r 0.994) . For samples containing iodine at <1.00 mu mol/L, the correlation bet ween values by both methods was still significant (r = 0.937). UI in a n iodine-deficient area in Ukraine, measured by this system, ranged fr om 0.06 to 1.83 mu mol/L (median 0.44 mu mol/L, n = 95), significantly lower than in Japan (range 0.23-50.70 mu mol/L, median 4.70 mu mol/L, n = 84) and consistent with mild iodine deficiency. This modified aut omated assay system, therefore, is useful and applicable for screening UI in inhabitants of iodine-deficient areas.