Determination of trace gold, platinum and palladium in geological samples by lead fire assay pre-concentration high resolution continuum source graphite furnace atomic absorption spectrometry
SUN Qiliang1,2,3,4, MAO Xiangju1,2,3,4, GUO Xiaorui1,2,3,4 ZHANG Hongli1,2,3,4, NI Wenshan*1,2,3,4
1. Zhengzhou Institute of Multipurpose Utilization of Mineral Resources, CAGS, Zhengzhou 450006, China; 2. Key Laboratory for Polymetallic Ores' Evaluation and Utilization, MNR, Zhengzhou 450006, China; 3. Key Laboratory of Comprehensive Utilization of Gold Resource in Henan Province, Zhengzhou 450006, China; 4. Northwest China Center for Geoscience Innovation, Xi'an 710054, China
Abstract：The abundance of gold (Au), platinum (Pt) and palladium (Pd) in natural ores is very low and the distribution is nonuniform. Due to the nugget effect, the accurate determination of their contents is always a challenge in analysis of geochemical samples. Au, Pt and Pd in samples were separated and enriched in alloy granule by lead fire assay method.The alloy granule was dissolved with aqua regia and then determined by high resolution continuum source graphite furnace atomic absorption spectrometry (HRCS-GFAAS). The determination method of trace Au, Pt and Pd in geochemical sample was established. The experiments indicated that: when the purified basic lead carbonate prepared in experiment was used to replace the commercial lead oxide agent as the trapping agent, the blank values of Au, Pt and Pd in lead fire assay could be greatly reduced and very stable. During the treatment of alloy granule, nitric acid was firstly used to dissolve the silver in alloy granule, then hydrochloric acid was added to form aqua regia to fully dissolve Au, Pt and Pd. NaCl solution was dropwise added to make Au, Pt and Pd exist in solution in the form of stable sodium halogenate. The high resolution beam splitting system of continuum source atomic absorption spectrometer was used. The resolutions of testing elements in spectra were all not more than 0.0014 9 nm/pixel, which guaranteed the complete separation of atomic absorption lines and interference lines of Au, Pt and Pd. The interference with lines of Au, Pt and Pd caused by coexisting elements in sample could be ignored. Under the selected experimental conditions,the calibration curves of Au,Pt and Pd were fitted by the least square method using the absorbances and the corresponding mass concentrations. The determination coefficient (R2) of calibration curve of Au,Pt and Pd was 0.999 6,0.999 9 and 0.999 9, respectively. The characteristic concentration was 0.341, 2.964 and 0.630 (ng/mL)/1%A. The proposed method was applied for the determination of Au, Pt and Pd in geochemical samples (soil matrix). The relative standard deviations (RSD,n=5) of determination results were between 6.2% and 9.6%. The experimental method was used to analyze Au, Pt and Pd in certified reference materials of soil and rock (olivinite and pyroxene), and the found results were in good agreement with the certified values.
孙启亮, 毛香菊, 郭晓瑞, 张宏丽, 倪文山. 铅试金富集-高分辨率连续光源石墨炉原子吸收光谱法测定地球化学样品中痕量金铂钯[J]. 冶金分析, 2021, 41(7): 10-16.
SUN Qiliang, MAO Xiangju, GUO Xiaorui ZHANG Hongli, NI Wenshan. Determination of trace gold, platinum and palladium in geological samples by lead fire assay pre-concentration high resolution continuum source graphite furnace atomic absorption spectrometry. , 2021, 41(7): 10-16.
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