Reduction of iodate in iodated salt to iodide during cooking with iodine as measured by an improved HPLC/ICP–MS method

Abstract

Background: Iodate is a strong oxidant, and some animal studies indicate that iodate intake may cause adverse effects. A key focus of the safety assessment of potassium iodate as a salt additive is determining whether iodate is safely reduced to iodide in food. Objective: To study the reduction of iodate in table salt to iodide and molecular iodine during cooking. Materials and Methods: Fifteen food samples cooked with and without iodated salt were prepared in duplicate. The iodine in the cooked food was extracted with deionized water. The iodine species in the extracts were determined by using an improved high-performance liquid chromatography/inductively coupled plasma–mass spectrometry (HPLC/ICP–MS). The cooking temperature and the pH of the food were determined. Results: The conversion rate of iodate in iodated salt to iodide and molecular iodine was 96.4%±14.7% during cooking, with 86.8%±14.5% of the iodate converted to iodide ions and 9.6% ±6.2% converted to molecular iodine to lose. The limit of detection, limit of quantification, relative standard deviation and recovery rate of the method HPLC/ICP–MS were 0.70 μg/L for I− (0.69 μg/L for IO3−), 2.10 μg/L for I− (2.06 μg/L for IO3−), 2.6% and 101.6%±2.6%, respectively. Conclusion: Almost all iodate added to food was converted into iodide and molecular iodine during cooking. The improved HPLC/ICP–MS was reliable in the determination of iodine species in food extracts.