Determination of trace platinum in geochemical sample by isotope dilution-laser ablation inductively coupled plasma mass spectrometry with antimony fire assay
WANG Tiantian1,2,3, MAO Xiangju1,2,3, GUO Xiaorui1,2,3, FAN Lei1,2,3, LIU Yan1,2,3, NI Wenshan*1,2,3
1. Zhengzhou Institute of Multipurpose Utilization of Mineral Resources,CAGS,Zhengzhou 450006,China; 2. China National Engineering Research Center for Utilization of Industrial Minerals,Zhengzhou 450006,China; 3. Key Laboratory for Polymetallic Ores' Evaluation and Utilization,Ministry of Natural Resources,Zhengzhou 450006,China
Abstract：The content of platinum is usually determined by inductively coupled plasma mass spectrometry (ICP-MS) after enrichment by fire assay. The assay button should be dissolved for determination, so the operation is complicated and there is solution dilution effect. In this study, 194Pt isotope diluent was added into the sample, and platinum was separated and enriched by antimony fire assay. The antimony composite granule was obtained after cupellation and then polished to antimony slice with smooth surface. The isotope ratio (195Pt/194Pt) was determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The content of platinum was quantified according to the formula of isotope dilution method. Thus, a determination method of trace platinum in geochemical samples was established with direct solid sampling after fire assay enrichment. The experiments showed that when self-purified antimony oxide was used as collector agent and high purity quartz crucible was used instead of traditional fire assay clay crucible, the blank value of platinum in antimony fire assay process could be reduced to 0.52 ng, which broke the bottleneck of high blank value for platinum in fire assay process. LA-ICP-MS planar imaging results showed that the distribution of 194Pt and 195Pt in antimony slice was not uniform, but the rules were similar for the trend of uneven distribution. LA-ICP-MS was used for the further multipoint ablation of 194Pt and 195Pt in antimony slice. The results showed that the relative standard deviations (RSDs,n=6) of mass spectral intensity of 194Pt and 195Pt were 14.7% and 14.1%,respectively. However, for the mass spectral intensity ratio of 195Pt and 194Pt, the RSD was 2.5%, indicating that platinum in isotope diluent had been fully exchanged with that in geochemical samples. The proposed method was applied for determination of platinum in geochemical certifeid reference materials, and the results were basically consistent with the certified values. The RSDs (n=6) of determination results were between 2.0% and 5.1%. The proposed method realized the determination of platinum in geochemical samples by solid-solid combined analysis technique (solid high temperature melting enrichment-laser ablation direct solid sampling) and isotope dilution.
王甜甜, 毛香菊, 郭晓瑞, 樊蕾, 刘闫, 倪文山. 锑试金-同位素稀释-激光剥蚀电感耦合等离子体质谱法测定地球化学样品中痕量铂[J]. 冶金分析, 2024, 44(9): 1-7.
WANG Tiantian, MAO Xiangju, GUO Xiaorui, FAN Lei, LIU Yan, NI Wenshan. Determination of trace platinum in geochemical sample by isotope dilution-laser ablation inductively coupled plasma mass spectrometry with antimony fire assay. , 2024, 44(9): 1-7.
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