Scholarly record

DETERMINATION OF ENVIRONMENTAL PLATINUM POLLUTION BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

ST. Palesskiy, I. Nikolaeva, O. Kozmenko

Abstract

The accurate determination of the platinum group elements (PGEs) in environmental samples has become a particularly important in the past few years with the introduction of new legislation regulating the fitting of catalytic converters to petrol vehicles [1]. The emission of PGEs autocatalysts represents a potentially, highly mobile source of environmental contamination. Pt, Pd and Rh from catalyst degradation are deposited along roadways. Although inert in metallic form, platinum salts pose a real health risk. This paper reports a simple analytical procedure for PGEs determination in geological and environmental samples using microwave acid digestion, separation of the PGEs by cation-exchange chromatography and analysis by isotope dilution inductively coupled plasma mass-spectrometry (ID-ICP-MS). Geological reference materials with lowabundance of PGEs were weighted into teflon vessels with spikes of PGEs. Acid digestion of these samples was carried out in the mixture of sub-boiled concentrated HCl and HNO3 (1:3) under the pressure (20 bar) and the temperature (200ºC) in hermetic teflon vessels of microwave accelerated reactive system MARS-5. After full spike-sample equilibration during sample digestion the obtained solutions were centrifuged to remove the solid residue. Cation exchange columns filled with Dowex AG50Wx8 resin (200-400 mesh) have been applied for PGE separation using 0.6M HCl as the mobile phase. Elimination of such cations as Zr and Hf decreases spectral interferences on PGE peaks in ICP-MS spectra. All ICP-MS isotopic analyses of spikes and spike-sample mixtures were performed by high resolution ICP mass-spectrometer ELEMENT Finnigan MAT with ultrasonic nebuliser U-5000AT+. Uncertainty of isotopic ratio determination was about 0.2\%. Concentrations of all elements were calculated with the known ID formula. 195Pt was used as the internal standard to calculate the abundances of monoisotope element Rh. Average total procedural blanks were 10-20 pg for all elements. The obtained PGEs concentrations in low-abundance reference materials – GP-13, UBN-1 and W-1 are compared with available data. The new ID-ICP-MS data are in good agreement with previously published values of PGEs in low-abundance reference materials. The concentrations of PGEs in environmental samples (road-side dusts and soil from Novosibirsk, Russia) were determined using proposed analytical procedure.

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