Determination of trace rhodium and iridium in geochemical samples by graphite furnace atomic absorption spectrometry with tin fire assay and microwave digestion
WANG Tiantian1,2,3, GUO Xiaorui1,2,3, MAO Xiangju1,2,3, SUN Qiliang1,2,3, ZHANG Hongli1,2,3, YAO Mingxing*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, MNR, Zhengzhou 450006, China
Abstract：Rhodium and iridium had an important strategic position in the industrial field. However, their contents in nature were extremely low with nonuniform distribution. The accurate determination of rhodium and iridium contents was always a difficulty in the analysis of geochemical samples. Trace rhodium and iridium in sample were enriched by tin fire assay. The tin button was pressed to tin sheet with press machine followed by dissolution with hydrochloric acid. After filtration, the precipitate and filter paper were treated by microwave digestion with aqua regia (1+1) as the medium. The contents of rhodium and iridium in sample solution were determined by graphite furnace atomic absorption spectrometry (GF-AAS). A determination method of rhodium and iridium in geochemical samples was established. The experimental results showed that the blank values of rhodium and iridium in process of tin fire assay were much lower than those in nickel fire assay and lead fire assay when tin powder was used as the collector. Under the selected experimental conditions, the calibration curves were fitted by the least square method of quadratic equation based on the absorbance of rhodium and iridium as well as their corresponding mass concentration in range of 12.5-50 ng/mL. The determination coefficients of the calibration curves were 0.999 6 and 0.999 2, respectively. The characteristic concentrations of rhodium and iridium were 0.183 ng/mL and 1.367 ng/mL, and the limits of detection were 0.015 ng/g and 0.018 ng/g, respectively. The experimental method was applied to the analysis of rhodium and iridium in certified reference materials of geochemical sample of platinum family elements. The results were in good agreement with the certified values. The relative standard deviations (RSDs, n=6) were between 3.6% and 12.6%. The proposed method was applied to the analysis of chromite and soil samples. The RSDs (n=6) of determination results were between 3.7% and 7.3%. The recoveries were between 85% and 108%.
王甜甜, 郭晓瑞, 毛香菊, 孙启亮, 张宏丽, 姚明星. 锡试金富集-微波消解-石墨炉原子吸收光谱法测定地球化学样品中痕量铑和铱[J]. 冶金分析, 2021, 41(9): 70-76.
WANG Tiantian, GUO Xiaorui, MAO Xiangju, SUN Qiliang, ZHANG Hongli, YAO Mingxing. Determination of trace rhodium and iridium in geochemical samples by graphite furnace atomic absorption spectrometry with tin fire assay and microwave digestion. , 2021, 41(9): 70-76.
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