Simultaneous determination of platinum group elements and rhenium in rock samples using isotope dilution inductively coupled plasma mass spectrometry after cation exchange separation followed by solvent extraction

摘要

A simple and precise determination method for platinum group elements (PGEs) and Re in rock samples was developed using isotope dilution coupled with inductively coupled plasma mass spectrometry (ID-ICP-MS).Cation exchange separation was employed for simplicity,because it is applicable to group separation and simultaneous isotopic measurement in contrast with the widely used anion exchange separation which entails separate elution.However,its application to ID-ICP-MS has been limited due to spectral interferences from impurities retained in the PGE fraction even after ion chromatography.To overcome this limitation,solvent extraction using N-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform was successfully applied for further purification.After the examination of optimum experimental parameters in cation exchange separation and solvent extraction using synthetic PGE solution,the established procedure was applied to the determination of PGEs and Re in some geochemical reference materials.The obtained results agreed well with the literature data determined using the different digestion methods (NiS fire assay and the use of a high-pressure asher) within the analytical uncertainties of each other.Significant difference in reproducibility between Ru,Ir,Pt and Os group,and Pd and Re group was observed in the results for BHVO-2 and JA-2.By considering the error factors affecting analytical reproducibility,we concluded that the difference is ascribed to the sample heterogeneity of minor minerals enriched in Ru,Ir,Pt and Os.