过氧化钠熔融-电感耦合等离子体质谱法测定黑钨矿中铊

黑钨矿中铊会污染土壤和水源,开采之前需要对黑钨矿中的铊含量进行检测。采用过氧化钠熔融分解样品,用30 mL硝酸浸取分解产物,选择²⁰⁵Tl为测定同位素,以10 ng/mL铱为内标进行校正,建立了电感耦合等离子体质谱法(ICP-MS)测定黑钨矿中铊的分析方法。对过氧化钠用量及熔融时间进行优化,结果发现,对于0.30 g样品,采用2.5 g过氧化钠于700 ℃熔融20 min后,样品中铊可被硝酸浸取完全。在优化的实验条件下,校准曲线相关系数为0.999 9,线性范围为0.05~10 ng/mL,方法检出限为0.03 μg/g,定量限为0.099 μg/g。按照实验方法对黑钨矿样品中铊进行测定,结果的相对标准偏差(RSD, n=11)小于3%。将实验方法应用于钨矿石成分分析标准物质中铊的测定,结果与认定值的相对误差小于5%。先用酸消解法处理黑钨矿样品,所得不溶物继续用过氧化钠熔融处理,合并两次分解所得溶液后用火焰原子吸收光谱法进行测定,结果与实验方法保持一致。

Determination of thallium in wolframite by inductively coupled plasma mass spectrometry after fusion with sodium peroxide

Thallium in wolframite could cause soil and water pollution. The content of thallium in wolframite must be detected before exploitation. The sample was decomposed by fusion method with sodium peroxide. The decomposition product was leached with 30 mL of nitric acid. ²⁰⁵Tl was selected as the determination isotope. Thus, an analysis method of thallium in wolframite by inductively coupled plasma mass spectrometry (ICP-MS) was established with 10 ng/mL of iridium as internal standard. The dosage of sodium peroxide and fusion time were optimized. It was found that the thallium in 0.3 g of sample could be fully leached by nitric acid after fusion with 2.5 g of sodium peroxide at 700 ℃ for 20 min. Under the optimized experimental conditions, the correlation coefficient of calibration curve was 0.999 9 with linear range of 0.05-10 ng/mL. The limit of detection was 0.03 μg/g, and the limit of quantification was 0.099 μg/g. The content of thallium in wolframite samples was determined according to the proposed method. The relative standard deviations (RSDs, n=11) of determination results were less than 3%. The proposed method was applied in determination of thallium in the certified reference materials of tungsten ore for composition analysis. The relative errors between the determination results and the certified values were less than 5%. Wolframite samples were treated with acid digestion method, and the insoluble substance was further fused with sodium peroxide. The solution obtained by two decomposition was merged and determined by flame atomic absorption spectrometry. The results were consistent with the proposed method.