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, followed by trapping the iodine on charcoal and quantifying the element by neutron activation analysis (NAA), has been used at the National Institute 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 range of certified reference materials (CRMs) and a powdered grass material that was prepared as an in-house reference material (RM). Because of the combustion step involved, samples with low or no fat content (e.g., cereal products, selected botanical specimens, and nonfat milk powder) and inorganic materials (e.g., coal fly ash and dried sediments) are more suited for analysis by this method. In general, the results for several types of samples obtained by this method agreed with those obtained by a second radiochemical (R) NAA, as well as by a third method using inductively coupled plasma mass spectrometry (ICP-MS). PC-NAA is a useful technique for determining iodine in biological and environmental samples, especially for verification of iodine results obtained from other methods.