SPECTROPHOTOMETRIC DETERMINATION OF THIOCYANATE BY ITS OXIDATION WITH IODATE

A simple method for the determination of thiocyanate has been proposed, based on the oxidation of thiocyanate to sulfate with iodate in a sulfuric acid medium and on the spectrophotometric measurement of the iodine as triiodide at 350 nm, formed from the excess iodate with iodide added. The complete oxidation of thiocyanate to sulfate using iodate was achieved in a medium containing varying amounts of sulfuric acid at 30-degrees-C. Thiocyanate reacted with iodate with a mole ratio of 1:1 under the conditions employed here. The proposed method is approximately 20-fold more sensitive than the conventional method using iron(III) and can be applied to the determination of thiocyanate in the concentration range 5.6X10(-7)-5.2X10(-5) mol dm-1 (0.31-30.2 mug of SCN- in 10 cm3). The relative standard deviation (n=11) was 0.44% at the 3X10(-5) mol dm-3 thiocyanate (17.4 mug of SCN- in 10 cm3) level.