QUANTITATIVE-DETERMINATION OF THE PLATINUM-GROUP ELEMENTS AND GOLD USING NIS FIRE ASSAY WITH LASER ABLATION-INDUCTIVELY COUPLED PLASMA-MASSSPECTROMETRY (LA-ICP-MS)

Traditional methods for separating the platinum-group elements (ruthen ium, rhodium, palladium, osmium, iridium, platinum; PGE's) and gold (A u) from ores and rocks have been adapted for use with laser ablation-i nductively coupled plasma-mass spectrometry (LA-ICP-MS). Samples were prepared using NiS fire-assay techniques resulting in the production o f a collector button weighing only similar to 1 g. The button was grou nd to produce a flat surface and directly ablated using a Nd:YAG laser operating at fundamental wavelength. Quantitative data were obtained by external calibration against both natural geological reference mate rials (SARM-7, MINTEK 2/77 and CHR-Pt+) and synthetic NiS standard but tons produced by doping high-purity quartz sand with multi-element sto ck solutions. Analysis times are rapid, 30 s per analysis, and the sam pling protocols developed offer the possibility of full automation. Pr ecision of the measurements varied according to concentration and the element concerned, but were typically 10-15% relative standard deviati on or better. Accuracy of the data was assessed by comparison of measu red and reference values. Accuracy was partly dependent on element. Da ta for Ru, Ph and Pd in 2/77 and Ru in CHR-Pt+ were in excellent agree ment with reference values, while recoveries for Ph in CHR-Pt+ were a little high. Data for Os and Au could only be evaluated in SARM-7 wher e agreement with reference values was good. Platinum consistently show ed poor recovery with values which were typically 30% low. Experimenta lly determined detection limits were similar for all elements, from 10 to 90 ng g(-1). The method provides for the rapid, simultaneous and s ensitive determination of the PGE's and Au in rocks and ores.