Highly selective first order derivative spectrophotometric determination of osmium(VIII) using anthranilic acid as a chromogenic reagent

A simple, selective and sensitive spectrophotometric method has been developed for the determination of osmium(VIII) using anthranilic acid as a reagent in the presence of Triton X-100. The molar absorptivity and Sandell's sensitivity of the violet coloured species are 3.03 x 10(4) L mol(-1) cm(-1) and 3.5 ng cm(-2) respectively. Beer's law is obeyed between 0.5-5.5 mu g mL(-1) of Os(VIII) at 500 nm. The stoichiometry of the complex is found to be 1:2 (metal: ligand). Calibration graph for the first order derivative spectrophotometric determination of Os(VIII) is derived by measuring derivative amplitudes at 525 nm with a linear range 0.25-5.5 mu g mL(-1). The detection limit and quantitation limit of first order derivative spectrophotometry are found to be 0.075 and 0.25 mu g mL(-1), respectively. The metal ions, which are normally associated with osmium in catalysts and alloy samples, do not interfere. The proposed method has been successfully applied for the trace level determination of osmium in various synthetic mixtures containing commonly associated metal ions and corresponding to the alloy composition.