高纯石英样品中放射性钍和铀含量的测量方法研究

Determination of Thorium and Uranium in High Purity Quartz Samples

针对半导体工业原料高纯石英砂,放射性元素钍和铀的含量是其中的一个需要关注的指标。建立了电感耦合等离子体质谱法(ICP-MS)测定高纯石英样品中放射性钍和铀的方法。称取一定质量的高纯石英样品后,加入氢氟酸和硝酸使其完全消解,蒸干后加入硝酸复溶杂质元素,最后用2%的硝酸溶液定容至5 mL,使用^(187)Re作为在线内标,测量^(232)Th和^(238)U。石英样品称样量可以多达1 g以上,测量样品溶液中盐含量较低,无需考虑基体效应。标准工作曲线的范围为0、0.05、0.1、0.2、0.5和1.0μg·L^(-1),工作曲线的相关系数均大于0.9995,该方法钍和铀的检出限分别为0.02和0.03 ng·g^(-1)。对钍、铀含量分别为0.32 ng·g^(-1)和0.62 ng·g^(-1)的样品,7次测量精密度分别为5.7%和7.7%,通过3组加标实验样品,钍和铀的平均加标回收率分别为94.8%和91.4%。该分析方法精密度和加标回收率符合一般化学分析方法验证的要求,可以应用于高纯石英样品中放射性钍和铀的测量,其他元素也可参考该方法进行测量。

The content of radioactive thorium and uranium in high purity quartz sand is an important indicator for the raw material of semiconductor industry.A method for the determination of thorium and uranium in high purity quartz samples by inductively coupled plasma mass spectrometry(ICP-MS)has been established.A certain quantity of high purity quartz sample was weighted and completely digested by hydrofluoric acid and nitric acid mix solution;the solution was evaporated to dryness and the impurity elements was finally dissolved by 5 mL 2%nitric acid solution.^(187)Re as the online internal standard was used to measure the isotope of ^(232)Th and^(238)U.The weight of the quartz samples was allowed to be over 1 g and the matrix effect was not considered due to the relatively low content of salt in the sample solution.The range of standard working curve was 0,0.05,0.1,0.2,0.5,1.0μg·L^(-1),the correlation coefficient of the working curve was greater than 0.9995.The detection limits of Th and U were 0.02 ng·g^(-1)and 0.03 ng·g^(-1) respectively.For the samples with 0.32 ng·g-1 and 0.62 ng·g^(-1) of thorium and uranium,the measurement precision in 7 times was 5.7%and 7.7%respectively.Through three groups of spiked experimental samples,the average spiked recoveries were 94.8%and 91.4%.The precision and standard addition recoveries meet the requirements of verification of common chemical analysis methods.Therefore,the method can be applied to the measurement of thorium uranium in high purity quartz samples and used as reference for digestion and measurement of other elements.