抄録
The largest fraction of the short-term and long-term dose from accidental releases and fallout from atomic bomb tests was from iodine isotopes. Among the radioisotopes of iodine, I-129 is of most concern due to its long half-live. It has been expected that the environmental behavior of radioactive I-129 should be basically similar to that of natural I-127. Thus, the biogeochemical cycling of stable iodine in the environment can be used for the safety assessment of I-129. We here report a hyphenation technical between HPLC and SF-ICP-MS for the speciation of stable iodine in seawater because the chemical form is one of the most important factors controlling iodine environmental behavior in the ocean. Several HPLC separation columns, including anion-exchange (ExcelPak ICS-A23), cation-exchange (IonPac CG5A) and size-exclusion (AsahiPak GS-220HQ) columns were investigated for their performance for separation of iodate and iodide. Surprisingly, it was found that the best separation was obtained with the short CG5A cation-exchange column with a TCC2 cation concentrator as the guard column. With a mobile phase of 30 mM ammonium carbonate at a flow rate of 1 ml/min, the analysis of iodate and iodide can be completed within 5 min. Seawater can be directed introduced into the HPLC column for analysis after a 5-fold dilution of seawater. The developed analytical method was successfully applied to the study on the vertical distribution of iodine species in coastal water off Aomori, Japan.
