Analysis of platinum concentrate by means of slurry nebulisation and inductively coupled plasma-optical emission spectrometry

Prior to final refining, Carius tubes are used during the routine analysis of platinum group metals (PGMs) and Au in precious metal concentrate (PMC). Samples of PMC contain about 60% PGMs and are difficult to dissolve. The current technique, using Carius tubes, is both time-consuming (taking up to 24 h) and hazardous. A method using slurry nebulisation and inductively coupled plasma-optical emission spectroscopy has been developed to replace this technique. Slurries for nebulisation consisted of 0.05% m/v sample, 0.5% m/v Triton X-100 and 5% v/v HCl. By using one sample (an in-house quality control sample), in which the concentrations of the elements of interest (Ag, As, Au, Bi, Cu, Fe, Ir, Ni, Pb, Pd, Pt, Rh, Ru, Se and Te) were known, for calibration, other samples could be analysed. Allowing for a grinding time of 30 min, the analysis of a PMC sample for all elements of interest could be completed in 90 min. Results obtained for Ag, Au, Cu, Fe, Ir, Ni, Pb, Pd, Pt, Rh, Ru, and Te were within the 95% confidence level of those obtained using the Carius tubes technique. Crystal inclusions in the ground sample may have influenced the determination of As, Bi and Se. Either Al or Si, which are elements used in two different mills (as carbide or agate), could not be determined accurately due to contamination.