Determination of platinum-group elements and rhenium in standard geological samples by isotope dilution with mass-spectrometric ending

A method is proposed for determining platinum-group elements, Ru, Pd, Os, Ir, Pt, and Re in geological samples by isotope dilution with mass spectrometric ending after sample decomposition with a mixture (1: 3) of conc. HCl + HNO(3) in a microwave system and the chromatographic separation of the analytes from the matrix on an AG 50W x 8 cation exchanger. The concentrations and isotope ratios are determined on high-resolution mass spectrometers ELEMENT and ELEMENT2. The attained detection limits range from 0.005 ng/g (Ir) to 0.2 ng/g (Pd) in solid samples. The use of isotope dilution improves the accuracy of determination and takes into account the matrix effect and changes in plasma parameters on the analytical signal. The method is tested in the analysis of standard samples of spinel lherzolite (GP-13) and serpentinite (UB-N). The relative standard deviation of the results of analysis is 5-22%, depending on the element and its concentration level (Ru, Pd, Re, Pt). In determining Os and Ir, a certain decrease in the accuracy and repeatability of the results is noticed.