Spectrophotometric determination of rhodium(III) in aqueous and alcoholic media using 2-thiobarbituric acid

Abstract

A spectrophotometric study of the rhodium(III)- 2-thiobarbituric acid system is presented. Rhodium(III) forms 1:2 and 1:4 complexes with 2-thiobarbituric acid in water and 98% ethanol, respectively. Conformity to Beer's law at 327 nm was observed for up to 14 µg ml^–1 of rhodium in water and for up to 12 µg ml^–1 in 98% ethanol and the detection limits were 0.24 and 0.34 µg ml^–1 of rhodium, respectively. Molar absorptivities at 327 nm in aqueous and alcoholic media were 1.04 × 10⁴ and 1.08 × 10⁴ l mol^–1 cm^–1 and Sandell's sensitivities were 0.0098 and 0.0095 µg cm^–2, respectively.

The tolerance of the system to platinum metals and other common cations is reported, the method is evaluated and a comparison with the main colorimetric methods for rhodium determination developed in recent years is presented.