Application of Thionine Dye for Highly Sensitive and Selective Catalytic kinetic Determination of Osmium

A new, highly sensitive and selective catalytic kinetic method (CKM) for determination of osmium (VIII) has been established based on its catalytic effect on the oxidation of thionine dye by hydrogen peroxide in alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance band of thionine at 600 nm. Under the optimum conditions, the proposed method allows determination of osmium concentrations in the range of 0.1 - 220 ng ml-1 with a detection limit of 0.015 ng ml-1. The relative standard deviations for 11 replicate determinations of 0.20, 2.0 and 20 ng ml-1 osmium (VIII) were 3.3, 1.0 and 0.69%, respectively. This method is free from of most interferences, highly selective, sensitive and very stable.