A rapid solvent extraction method for the determination of radio-iodine in sea water.

A solvent extraction procedure for the determination of radio-iodine in sea water is described. The water is treated with alkaline permanganate to remove algae, and, after removal of permanganate, the iodide is oxidized to iodine for extraction into toluene. The radio-iodine with carrier is stripped from the solvent then re-extracted into a smaller volume of toluene for liquid scintillation counting and colorimetric determination of carrier recovery as iodine. 2-Methyl-1-butene is used to decolorize the toluene-iodine solution under u.v. light and avoid colour quenching during counting. Samples spiked with iodine-131 showed essentially quantitative recovery from 1.0 l of sea water with a typical recovery of 80–85% of carrier. The method is applicable in the presence of high concentrations of many foreign ions and the decontamination factor for a number of radionuclides is greater than 10³. The limit of detection is less than 5.0 · 10^-9 μCi ml^-1.