DIRECT DETERMINATION OF URINARY IODINE BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY USING ISOTOPE-DILUTION WITH I-129

An inductively coupled mass spectrometric method was developed for the direct determination of iodine in urine. The application of isotope d ilution analysis with added I-129 offers new possibilities for automat ic and accurate determinations. The sample preparation consists of dil ution with an ammonia solution containing I-129. The validation was ma de by comparison with the results obtained in another laboratory by a spectrophotometric method based on the Sandell-Kolthoff reaction. Diff erent regression models, including maximum likelihood estimation, were used to compare the methods. None of the models revealed analytical b ias between the two methods. The urine samples analyzed for validation were from three persons previously exposed to an iodine bath and cove red a concentration range of 0.2 to 2.8 mu mol/L. A detection limit of 0.02 mu mol/L, a within-run CV of 2.5%, and a between-run CV of 11.9% were estimated for the proposed method.