Determination of Platinum-Group Elements in Geological Samples by Isotope Dilution-Inductively Coupled Plasma-Mass Spectrometry Combined with Sulfide Fire Assay Preconcentration

摘要

A method was developed for the determination of platinum-group elements (PGE) in geological samples by isotope dilution-inductively coupled plasma-mass spectrometry combined with sulfide fire assay preconcentration. Samples were fused and PGE analytes were concentrated in sulfide buttons. The buttons were dissolved using HCl leaving PGE analytes in insoluble residues, which were digested in HNO3 and simultaneously processed for the distillation of Os. The remaining solutions were further prepared for the purification of Ru, Rh, Pd, Ir and Pt using a tandem assembly of cation and Ln resin columns. The eluents were directly analysed by membrane desolvation-ICP-MS. Ruthenium, Pd, Os, Ir and Pt were determined by isotope dilution, whereas Rh was determined by conventional reference material calibration combined with Ir-193 as the internal standard element. The method was validated using a series of PGE reference materials, and the measurement data were consistent with the recommended and the literature values. The measurement precision was better than 10% RSD. The procedural blanks were 0.121ng for Ru, 0.204 for Rh, 0.960ng for Pd, 0.111ng for Os, 0.045ng for Ir and 0.661ng for Pt, and the limits of detection (3s) were 0.011ng g(-1) for Ru, 0.008ng g(-1) for Rh, 0.045ng g(-1) for Pd, 0.009ng g(-1) for Os, 0.006ng g(-1) for Ir and 0.016ng g(-1) for Pt when a test portion mass of 10g was used. This indicates that the proposed method can be used for the determination of trace amounts of PGE in geological samples.