Separation of trace amounts of rhodium(III) with tri-n-butyl phosphate from nitric acid and sodium trichloroacetate media

A new method for the quantitative extraction and separation of trace amounts of rhodium from nitric acid and sodium trichloroacetate media has been established based on the formation of an ion-association complex of hexahydrated rhodium cation Rh(H₂O)₆ ³⁺ and the trichloroacetate (TCA) anion in tri-n-butyl phosphate (TBP). The effect of various factors (solvent, pH, sodium trichloroacetate, shaking time, phase volume ratio, composition of the extracted species, foreign ions, transformation of rhodium chlorocomplexes into hexahydrated cation, etc.) on the extraction and back-extraction of rhodium has been investigated. The method can be combined with subsequent FAAS determination of rhodium. The procedure was applied to determine rhodium traces in chloroplatinic acid and palladium chloride. Received: 17 March 2000 / Revised: 15 May 2000 / Accepted: 19 May 2000