Improved accuracy in measurement of iodine in animal feeds by ICP/MS with alkaline dissolution

Abstract Despite its significance for animal health and disease prevention, iodine is generally not measured by feed laboratories in part due to the inadequacies of acidic digestion procedures used for other trace and macro minerals. Our lab has investigated whether simple alkaline dissolution of feeds significantly enhances iodine recovery and quantitation, as determined by monitoring of 127I on Inductively Coupled Plasma Mass Spectrometry, ICP/MS. We describe herein a simple alkaline dissolution procedure and its applicability to animal feeds for the accurate measurement of iodine along with a comparative analysis to acidic digestion techniques routinely applied to measurement of trace nutrient minerals such as cobalt, copper, molybdenum, selenium, and zinc using multi-laboratory proficiency tested feeds and standard reference materials. The improved alkaline dissolution method was found to yield iodine recoveries ranging from 98.2 – 101.3%, a significant improvement over acid digestion which yielded recoveries of only 40.9 – 63.9%. This contrasted with trace nutrient elements Co, Cu, Mo, Se and Zn which had excellent recoveries in acid digests, but only 36 – 88% recoveries in alkali.