TOTAL IODINE IN NUTRITIONAL AND BIOLOGICAL REFERENCE MATERIALS USING NEUTRON-ACTIVATION ANALYSIS AND INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

In a recent collaborative study intended to extend the variety of refe rence materials certified for iodine, three mineralization methods wer e developed to quantify the total iodine content of biological and nut ritional materials by inductively coupled plasma mass spectrometry (IC P-MS). A mixture of water-soluble tertiary amines was used as the matr ix solution for two oxygen combustion methods and for a simple extract ion at room temperature. Calibrations with matrix-matched standards, i nternal calibration, and isotope dilution with I-129 were used. Good a greement between neutron activation analysis (NAA) and the two combust ion methods was observed except for < 0.1 mg kg(-1) iodine concentrati ons. The amine extraction method gave the most reliable results for th e mixed diet, milk powder, and infant formula samples but low recoveri es for other biological materials owing to an incomplete extraction an d solubilization of iodine. The NAA method, with its freedom from reag ent blank, is a useful technique for the independent determination of iodine in biological, environmental and food matrices, especially for verification of iodine results obtained by ICP-MS.