Determination of chemical species of iodine in seawater by radiochemical neutron activation analysis combined with ion-exchange preseparation

A method for the determination of iodide, iodate, organic iodine, and total iodine in seawater was developed. The behaviors of loading, washing, and e luting of iodide, iodate, acid organic iodine in a strongly basic anion-exc hange column (AG1-x4, chlorine form) were studied by I-131 tracer. Iodide w as separated from other iodine species and other ions by directly passing f iltered natural seawater through an anion-exchange column, washing with dei onized water and 0.5 mol/L KNO3 solution, and eluting with 2.0 mol/L KNO3. Organic iodine was separated by passing seawater through an ion-exchange co lumn after iodate had been converted to iodide by KHSO3 and collecting effl uent during loading and washing with deionized water. The iodine content wa s determined by neutron activation analysis with postirradiation separation using CCl4 extraction. Studies of the effect of chlorine, bromine, and iod ine concentrations on the extraction separation show that the recovery of i odine decreases with increasing Br- and Cl- concentrations and decreasing I - concentration. Under the experimental conditions, iodine in seawater was quantitatively recovered, and a 0.2 mu g/L detection limit for iodine was o btained. Concentrations of total iodine, I-, IO3-, anti organic iodine in s eawater collected from Roskilde Fjord, Denmark, were determined.