Thiobarbituric acid as a reagent for the spectrophotometric determination of osmium

Abstract

A sensitive method for the spectrophotometric determination of osmium(VIII) has been developed. Osmium(VIII) reacts with 2-thiobarbituric acid, after heating at 80 °C for 30 min, to form a 1 : 4 complex with an absorption maximum at 332 nm. The molar absorptivity of the complex is 1.4 × 10⁶ l mol^–1 cm^–1 and the Sandell sensitivity of the reaction is 1.3 × 10^–4µg cm^–2 per 0.001 absorbance unit. Conformity to Beer's law was observed for up to 0.25 p.p.m. of osmium and the detection limit was calculated to be 0.005 p.p.m. The tolerance to platinum metals and other common ions was very satisfactory.