Extraction spectrophotometric determination of rhodium(III) with o-methylphenyl thiourea

Trivalent rhodium was determined spectrophotometrically as its 1:2 rhodium o-methylphenyl thiourea (OMPT) complex, extracted into chloroform from aqueous acetate buffer media at pH 5.4. The complex exhibits maximum absorption at 320 nm (Molar absorptivity 9.76 × 103 L mol−1 cm−1), Sandell’s sensitivity 0.0105 μg of rhodium(III) cm−2. Beer’s law obeyed up to 10.0 μg/ml. The method is free from a large number of interferences from cations and anions. The method is simple, selective and reproducible. It permits separation and determination of rhodium(III) from synthetic mixtures corresponding to alloys. A scheme for mutual separation of palladium(II), rhodium(III), platinum(IV) and iridium(III) has been developed.