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)

Abstract

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 l⁻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 × 10³ 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.

Keywords:

• osmium(IV)
• spectrophotometry
• ternary mixture separation

Acknowledgement

The authors are thankful to the Management of Pravara Rural Education Society and the Principal, Arts, Commerce and Science College Satral for providing necessary facilities in the department.