Development of a reliable analytical method for extraction spectrophotometric determination of ruthenium(III) from catalyst and fissium alloy using o-methylphenyl thiourea as a chromogenic chelating ligand

A simple and selective method is developed for the extraction spectrophotometric determination of ruthenium(III) using o-methylphenyl thiourea (OMPT) as a chromogenic chelating ligand. The basis of the proposed method is ruthenium(III)–OMPT complex formation in aqueous hydrochloric acid media (3.0 mol L−1) after 5.0 min heating on a boiling water bath and the complex formed is extracted into chloroform. The absorbance of green colored ruthenium(III)–OMPT complex is measured at 590 nm against the reagent blank. Beer’s law was obeyed up to 42.5 μg mL−1 of ruthenium(III) and the optimum concentration range is 7.56–39.81 μg mL−1 of ruthenium(III) as evaluated by Ringbom’s plot. Molar absorptivity and Sandell’s sensitivity of ruthenium(III)–OMPT complex in chloroform are 2.34 × 103 L mol−1 cm−1 and 0.043 μg cm−2 respectively. The composition of ruthenium(III):OMPT complex (1:2) was established from slope ratio method, mole ratio method and Job’s continuous variation method. Complex was stable for more than 48 h. The interfering effect of various foreign ions was studied and suitable masking agents are used wherever necessary to enhance the selectivity of the method. Proposed method is successfully applied for determination of ruthenium(III) from binary and ternary synthetic mixtures, synthetic mixtures corresponding to fissium alloy and ruthenium catalyst. Repetition of the method was checked by finding relative standard deviation (R.S.D) for 10 determinations which was 0.23%. A scheme for sequential separation of palladium(II), ruthenium(III), rhodium(III) and platinum(IV) has been developed.

Structure of ruthenium(III)–OMPT (1:2) complexFigure optionsDownload as PowerPoint slideHighlights
► Selective separation and determination of ruthenium(III).
► Low reagent concentration required for quantitative recovery.
► Method is free of interference from large number of foreign ions.
► Analysis: catalyst, fissium alloy, synthetic mixtures.
► Sequential separation: palladium(II), ruthenium(III), rhodium(III) and platinum(IV).