Determination of platinum group elements and gold in geological materials using an ultraviolet laser ablation high-resolution inductively coupled plasma mass spectrometric technique

Abstract

In this work, a UV laser system coupled to high-resolution ICP-MS was used in the determination of platinum group elements (PGE) and gold in nickel sulfide buttons prepared by the fire assay technique. A Nd:YAG laser operating at 266 nm quadrupled frequency was used. The laser operating parameters were established by studying signal intensity and the precision for different energy beams and frequencies. TheF-test was used to evaluate the homogeneity of the buttons, demonstrating that for most elements the distribution is homogeneous. The analyses were performed on three different sites in three replicates of the materials. The detection limits obtained (3σ) were in a range from 0.2 for Os (and Ir) to 7 ng g^–1 for Pt. The accuracy of the results was better than 16.7% for most elements. The effects of isobaric interference on the ¹⁰³Rh signal (²⁰⁶Pb²⁺ and ⁴⁰Ar⁶³Cu⁺) were evaluated by analysing NiS buttons doped with lead and copper. For Au, Pt and Pd, the standard deviations obtained were higher than expected and are related to a non-homogeneous distribution of these elements in the buttons. The concentrations of the elements in the geological reference materials UMT-1 and WPR-1 were obtained by external calibration curves.