Determination of iodide in seawater by ion chromatography

A simple and highly sensitive ion chromatographic method with UV detection was developed for iodide (I-) in seawater. A high-capacity anion-exchange resin with polystyrene-divinylbenzene matrix was used for both preconcentration and separation of iodide. Iodide in artificial seawater (salinity, 35 parts per thousand) was trapped quantitatively (98.8 +/- 0.6%) without peak broadening on a preconcentrator column and was separated with 0.35 M NaClO4 +/- 0.01 M phosphate buffer (pH 6.1). On the other hand, the major anions in seawater, chloride and sulfate ions, were partially trapped (5-20%) and did not interfere in the determination of I-. The detection limit for I- was 0.2 mu g/L for 6 mt of artificial seawater. The present method was applied to determination of I- (ND - 18.3 mu g/L) and total inorganic iodine (I- + IO3- - I, 50.0-52.7 mu g/L) in seawater samples taken near Japan.