Rapid and selective determination of osmium(Ⅳ) by UV-visible spectrophotometry using o-methylphenyl thiourea as a chromogenic chelating ligand: sequential separation of osmium(Ⅳ), rhodium(Ⅲ) and platinum(Ⅳ)

摘要

The objective of this research work was to develop a simple, highly sensitive and precise method for spectrophotometric determination of osmium(Ⅳ). O-Methylphenyl thiourea (OMPT) coordinates with osmium(Ⅳ) as a 1:1 (osmium(Ⅳ)-OMPT) complex in hydrochloric acid media (0.8 mol 1~(-1)). The novelty of the investigated method is instant complex formation at room temperature with no need of heating or standing. The complex is stable for more than 8 days. The method is applicable over a wide linearity range (up to 110 μg ml~(-1)). A low reagent concentration is required (2 ml, 0.009 mol l~(-1) in ethanol). The complex exhibits maximum absorption in the range of wavelength 510-522 nm and 514 nm was selected for further study. The molar absorptivity was 1.864 × 10~3 l moL~(-1) cm~(-1), Sandell's sensitivity was 0.102 μg of osmium(Ⅳ) cm~(-2). Proposed method was successfully applied for separation and determination of osmium(Ⅳ) from binary and ternary synthetic mixtures containing associated metal ions. A scheme for mutual separation of osmium(Ⅳ), rhodium (Ⅲ) and platinum(Ⅳ) is developed.