THE APPLICATION OF PREIRRADIATION COMBUSTION AND NEUTRON-ACTIVATION ANALYSIS TECHNIQUE FOR THE DETERMINATION OF IODINE IN FOOD AND ENVIRONMENTAL REFERENCE MATERIALS

The pre-irradiation combustion (PC) of samples to liberate iodine, fol lowed by trapping the iodine on charcoal and quantifying the element b y neutron activation analysis (NAA), has been used at the National Ins titute of Standards and Technology for the determination of iodine in biological materials. The applicability of this technique to numerous environmental and dietary matrices is illustrated by analysis of a ran ge of certified reference materials (CRMs) and a powdered grass materi al that was prepared as an in-house reference material (RM). Because o f the combustion step involved, samples with low or no fat content (e. g., cereal products, selected botanical specimens, and nonfat milk pow der) and inorganic materials (e.g., coal fly ash and dried sediments) are more suited for analysis by this method. In general, the results f or several types of samples obtained by this method agreed with those obtained by a second radiochemical (R) NAA, as well as by a third meth od using inductively coupled plasma mass spectrometry (ICP-MS). PC-NAA is a useful technique for determining iodine in biological and enviro nmental samples, especially for verification of iodine results obtaine d from other methods.