Determination of Rh, Pd and Pt in environmental silica containing matrices: capabilities and limitations of ICP-SFMS

Abstract

Quantification of three platinum group elements most relevant to environmental monitoring, i.e. Pt, Rh and Pd, was performed in road dust, exploiting the high mass resolution capabilities of ICP-SFMS (ELEMENT, Finnigan MAT, Bremen, Germany). Sample preparation involved complete microwave assisted acid digestion of the silicate matrix with HNO3–HCl–HF mixtures. A USN6000AT+ ultrasonic nebulizer (Cetac Technologies, Omaha, NE, USA) incorporating a membrane desolvation unit was used as the introduction system. For Pt the Hf oxide interference could be eliminated effectively by membrane desolvation alone. For Rh and Pd, interferences, which could not be eliminated by mass resolution, were evaluated carefully by standard addition of the concomitant ions. It could be shown that no mathematical correction of the result was necessary for Rh, provided that membrane desolvation was employed. Pd in turn could not be measured interference free with this instrumental set-up. A mathematical correction procedure was developed for Sr. Concentrations of 63 ng g−1 Pt, 9 ng g−1 Rh and 17 ng g−1 Pd were found in the road dust samples. The limits of detection were 0.4 ng g−1 for Pt, 0.1 ng g−1 for Rh and 0.5 for Pd. The overall method precision determined for six samples ranged from 6% (Pt) to 13% (Pd).