Determination of iodine in food samples by inductively coupled plasma mass spectrometry after alkaline extraction

Abstract

The development and application of a simple alkaline extraction method employing tetramethylammonium hydroxide (TMAH) and ICP-MS for the determination of iodine are described. Iodine, as naturally contained in Milk Powder, Egg Powder, Cod Muscle, Pig Kidney and Hay Powder, was extracted quantitatively at elevated temperatures (90 °C). A complete extraction of iodine from algae powder was achieved only if the particle size of the sample was below 300 µm. The applicability of the method was demonstrated by a round-robin test on two dietetic child nutrition food samples enriched artificially with iodine. All the iodine present in the samples was extracted completely by TMAH. The results were confirmed by decomposition of the samples. Consequently, the procedure was accepted as a German reference method for the determination of iodine in dietetic foodstuffs. The limit of determination, based on nine standard deviations of the blank, was 30 ng g^–1 (dry sample, 100 mg sample mass). Advice is given on preventing sources of error and contamination.