SPECTROPHOTOMETRIC REACTION-RATE METHOD FOR THE DETERMINATION OF OSMIUM BY ITS CATALYTIC EFFECT ON THE OXIDATION OF GALLOCYANINE BY BROMATE

A simple kinetic spectrophotometric method was developed for the deter mination of osmium. The method is based on the catalytic effect of osm ium as osmium tetroxide on the oxidation of gallocyanine by bromate at pH 7. The reaction is monitored spectrophotometrically by measuring t he decreasing absorbance of gallocyanine at 620 nm by the fixed-time m ethod. A detection limit of 0.01 ng/ml and linear calibration curve fr om 0.1 to 100 and from 100 to 1200 ng/ml Os(VIII) is reported. The rel ative standard deviation for 0.0100 mu g/ml Os(VIII) is 0.8% (N = 10). The method is free from most interferences. Osmium in synthetic sampl es is determined by this method, with satisfactory results.