Determination of the precious metals in milligram samples of sulfides and oxides using inductively coupled plasma mass spectrometry after ion exchange preconcentration

A method for the quantitative separation of six precious metals (Ru, Ph, Pd, Ir, Pt and Au) from large amounts of; transition elements (especially Fe, Ni, Cu and Zn) in dilute hydrochloric acid solutions using a strongly acidic cation exchange-resin, Amberlite CG-120, is described. The method has been applied to the determination of precious metals in small amounts (2-20 mg)of high purity sulfide and oxide mineral separates using inductively coupled plasma mass spectrometry (ICP-MS). Solid limits of detection for a 20 mg sample are less than 4 ng g(-1) for Ru, Ph, Ir, Pt, and Au, and 29 ng g-1. for Pd. Precision and accuracy are demonstrated by replicate analyses of sub-samples of a nickel sulfide fire assay bead of the reference material, SARM-7, which show good agreement with certified values and relative standard deviations of less than 8%. Poorer precision and accuracy was obtained for Au because of heterogeneity and inefficient collection in the nickel sulfide bead. Analyses of sulfide and magnetite minerals from Sudbury, Canada, copper-nickel sulphide ores demonstrate the method's usefulness in studying the genesis of precious metal ore deposits.