The method for determining iodine in drinking water using ICP-MS was developed, validated, and tested in our laboratory, and the results were previously published . In summary, the samples were diluted twice with an alkali matrix (2% NH4OH+0.1% EDTA). It should be noted that the method's limit of quantification (LOQ) <0.1 µg I L -1 , as reported by us previously, takes into account the sample dilution (at least twice) and possible memory effect that may occur when measuring relatively high-concentration samples (more than 1 µg I L -1 ). However, if the sample introduction system is clean and free of iodine residues, the instrument LOQ derived from calibration (0.1-5 µg I L -1 ) is 0.009 µg I L -1 , and the recoveries of control standards at 0.025 and 0.05 µg I L -1 are 85.6% and 97.2%, respectively. Thus, it is possible to measure concentrations of about 0.02 µg I L -1 with higher reliability in the low- concentrated samples diluted by a factor of 2 and achieve an actual method LOQ of 0.04 µg I L -1 , which is even slightly better.