Influence of preparation and analysis methods on determination of Rh, Pd and Pt content in automotive catalysts samples

Abstract

Use of catalytic converters is of great importance in modern transportation allowing conversion of exhaust gases produced during combustion of fuel into less toxic pollutants. The catalysts itself are mostly precious metals dispersed onto catalyst carrier which should be mechanically resistant and guarantee high surface area required for effective utilization of catalytic converter. Precious metals like rhodium, palladium and platinum commonly used in automotive catalytic converters are expensive and their content remains important even in scrapped converters from which they are extracted. In this paper various approaches for determination of precious metals in used and unused automotive catalysts were described. Two analytical techniques were applied: Inductively Coupled Plasma Optical Emission Spectrometry and Wavelength Dispersive X-Ray Fluorescence and three methods of sample preparation differing in terms of time and cost: (a) microwave-assisted digestion with inorganic acids, (b) fusion with flux and (c) pressed powder method. The latter two methods were used for WD XRF measurements while the first one for the ICP OES. Statistical data analysis was applied in order to assess accuracy and precision of the results obtained and to compare different sample preparation and analytical techniques. Repeatability of sample preparation and measurement, calibration curves, selectivity and recovery were presented.