INSTRUMENTAL AND RADIOCHEMICAL NEUTRON-ACTIVATION ANALYSIS OF TRACE IODINE IN GEOLOGICAL SAMPLES

For determining trace amounts of iodine in geological samples (igneous and sedimentary rocks), applicabilities of instrumental and radiochemical neutron activation analyses (NAA) using a short-lived nuclide I-128 were examined. Instrumental NAA using a TRIGA-type reactor and Cd metal or boron carbide as an absorbing filter of thermal neutron could be applied for the determination of iodine in ppm level in sedimentary rocks. Further, radiochemical NAA (RNAA) could lower the detection limit down to several ppb for igneous rock samples. Even though RNAA was employed, at least 6 samples could be routinely analyzed a day (6 h in reactor operation) using the analytical procedures reported in this work.