Determination of platinum in roadside dust samples by dynamic reaction cell-inductively coupled plasma-mass spectrometry

Abstract

The development of an analytical method for the determination of platinum (Pt) in environmental samples has been of concern in recent years because vehicles fitted with catalytic converters are spreading this element throughout the environment. A method for analysing low concentrations of Pt in roadside dust by dynamic reaction cell (DRC)-inductively coupled plasma mass spectrometry (ICP-MS), employing NH₃ reaction gas, is presented herein. The use of DRC technology permits the removal of the interfering species HfO⁺ in Pt determination. The analysis of dust, collected by a modified vacuum cleaner at the roadside, employed digestion in a microwave oven by aqua regia, with subsequent filtration. The detection limit obtained was in the region of 8–10 ng g⁻¹ for different Pt isotopes. The certified reference materials, NIST 2557 for auto catalyst and BCR 723 for road dust, were used to monitor the recovery of Pt in the method. Our results show that the conventional ICP-MS empirical corrections for such isobaric interferences of Pt may be inaccurate. Results are presented for Pt concentrations in road dust at various sampling locations in Hong Kong and these are highly correlated with vehicle traffic densities, but are not significantly correlated with the expected vehicle tracer species.