Kinetic spectrophotometric determination of thiocyanate based on its inhibitory effect on the oxidation of methyl red by bromate

A kinetic spectrophotometric method for measuring thiocyanate is described. The proposed method is based on the inhibitory effect of thiocyanate on the oxidation of Methyl Red by bromate in the presence of nitrite, which was monitored at 520 nm. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. Thiocyanate can be measured in the range of 0.05 - 1.1 mug ml(-1) with a detection limit of 0.025 mug ml(-1). This method has been used to determine trace thiocyanate in urine and tap water samples.