Analytical validation of an inductively coupled plasma mass spectrometry method for urinary iodine concentration measurements in Taiwan

Background: Urinary iodine concentration (UIC) measured by Sandell-Kolthoff spectrophotometric method has been used in the Nutrition and Health Surveys in Taiwan but this method is time consuming and produces toxic waste from arsenic trioxide. The aim of this study was to develop and validate an inductively coupled plasma mass spectrometry (ICP-MS) system to determine UIC in Taiwan. Methods: Samples and iodine calibrators were diluted 100-fold into an aqueous solution containing Triton X-100, 0.5% ammonia solution, and tellurium (128Te) as an internal standard. Digestion prior to analysis was not necessary. Precision, accuracy, serial dilution, and recovery tests were performed. A total of 1243 urine samples covering a wide range of iodine concentrations were measured by both Sandell-Kolthoff method and ICP-MS. Passing-Bablok regression and Bland–Altman plots were used to compare values across methods. Results: The limit for detection and quantification by ICP-MS was 0.95 μg/L and 2.85 μg/L, respectively. The intra-assay and inter-assay coefficients were