Spectrophotometric study of the ruthenium(III)-2-thiobarbituric acid system

Abstract

Ruthenium(III) forms a 1:2 complex with 2-thiobarbituric acid, with an absorption maximum at 338 nm; the molar absorptivity is 1.1 × 10⁴ l mol^–1 cm^–1 and the Sandell's sensitivity of the reaction is 0.0091 µg cm^–2 per 0.001 absorbance unit. Beer's law is obeyed for up to 28 µg ml^–1 of ruthenium. The molar composition of the complex was determined by the molar ratio method and confirmed by means of elemental analysis. Coordinate bonding involving the sulphur atom of 2-thiobarbituric acid was proved by infrared spectroscopy. The tolerance of the system to platinum metals and other common cations is reported.

A statistical evaluation of the proposed method has been undertaken and a comparison with important spectrophotometric reagents for ruthenium(III) used in recent years is presented.