Extraction complexes rhodium(III) with PAR in aqueous segregable systems with following spectrophotometric determination

Abstract

A two-phase aqueous system of polyethylene glycol (PEG), isopropanol- water - ammonium sulfate - 4- (2-pyridylazo) resorcinol (PAR) for extraction and spectrophotometric determination of rhodium(III). Rhodium(III) complex with PAR is extracted by ethanol, isopropanol, PEG-2000, PEG-115 with 96-99%
completeness. The interphase rhodium(III) complex with PAR was investigated by atomic absorption method and spectrophotometric method with SnCl₂. Was proposed the influence of pH, PAR concentration, nature of water-soluble extractant on the extraction completeness and spectrophotometric characteristics of rhodium(III) reaction with PAR in concentrated sulfate solutions was established. The composition of the extracted compound was established by the methods of equilibrium shift and molecular absorption spectrophotometry. By the method of equilibrium shift and molecular absorption spectrophotometry and it was found that the extracted compound includes [RhR₂]^_-, where R is a two-charge anion of PAR. In organic phase absorption
spectrums the increase of light absorption is observed compared with water phas(λ=520 nm) as well as 20 nm maximum shift in long wave region which is connected with absolute concentration, complex solvatation by solvent molecules. Using rhodium(III) extraction optimal conditions and pH=7 the extraction of platinum, ruthenium(IV), palladium is 6; 16 and 98%, accordingly. An alternative rhodium(III) extractionphotometric determination with PAR on the basis of PEG and water-soluble alcohols is proposed. The lineardependence is observed in the range of 0.2 – 2.0 rhodium microgrammes per ml. The relative standard deviation does not exceed 0.06.