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.

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