An automated method for the determination of iodine in geochemical samples

A method is described for the determination of iodine in natural waters, rocks, soils and plant material. The method is based on the Sandell-Kolthoff reaction, using the catalytic action of iodine on the reaction between As³⁺ and Ce⁴⁺ and has been adopted for use with the Technicon® autoanalyzer. The procedure is rapid enough to determine 100 to 125 samples per 40-hour week. As little as 0.04 ppm I can be determined in the samples with no pre-concentration, following fusion with NaK carbonate and MgO. The precision of the method is such that a rock sample containing 0.22 ppm I was determined with a coefficient of variation of 25.9% while a rock with 4.46 ppm I showed a coefficient of variation of 5.08%. The method is ideally suited to geochemical prospecting.