低射频功率-电感耦合等离子体质谱法测定高纯石英样品中痕量钾

碱金属元素钾作为高纯石英产品中重要的杂质元素，其含量的准确测定对科学评价、开发高纯石英产品意义重大。采用常压混酸浸取—高温挥发除酸的方式进行高纯石英样品的化学前处理，基于电感耦合等离子体质谱仪，在低射频功率下，以50 ng/mL铷为内标元素，大幅消除了钾元素测定中背景产生的质谱干扰，实现了高纯石英样品中痕量钾元素的测定。对测试过程中的样品称样量、质谱测定中的射频功率、采样深度、载气流速等进行了条件优化。最终在称样量1.000 0 g、射频功率800 W、采样深度5.6 mm、载气流速1.06 L/min的最优条件下，经测定钾质量浓度在0.100~50 ng/mL范围内与其质谱强度呈线性相关，相关系数为0.999 6。以1.000 0 g称样量计，方法对高纯石英中钾的检出限为0.057 μg/g，定量限为0.191 μg/g。选择典型商品化高纯石英样品进行本方法的应用试验，每个样品平行测定9次，并进行加标回收率试验和方法比对试验，测定值与石墨炉原子吸收光谱法的测定结果基本一致，相对标准偏差(RSD)在2.9%~5.1%之间，加标回收率在96.4%~105.4%之间。 

Determination of Ultra-trace Potassium in High Purity Quartz by Low RF Power-Inductively Coupled Plasma Mass Spectrometry

Potassium (K) is an important impurity element in high-purity quartz and accurate determination of its content is of great significance for the evaluation of the quality of high-purity quartz products. Via ultra-trace K in high-purity quartz samples were dissolved by atmospheric acid dissolution method, an inductively coupled plasma mass spectrometry (ICP-MS) determination method for K was established and the interference of multi-atomic molecular ions was eliminated by cold plasma with low RF power in ICP-MS and 50 ng/mL rubidium was used as the internal standard elements in this process. Background interference in mass spectrometry for the determination of potassium was greatly eliminates. And the sample weight, RF power, sampling depth and atomized gas flow were optimized in this work. Finally, under the optimal conditions of 1.000 0 g of weight sample, 800 W of RF power, 5.6 mm of sampling depth and 1.06 L/min of atomized gas flow rate, K element standard series solutions were determined and the mass spectrometry intensity of K showed good linear relationship with ρ(K) in the range of 0.100~50 ng/mL with the correlation coefficients of calibration curve was 0.999 6. The detection limit and quantification limit of K in high-purity quartz were 0.057 μg/g and 0.191 μg/g, respectively. Typical commercial high-purity quartz samples were selected for the application experiment of this method, and the relative standard deviations (RSD) for 9 parallel measurements were between 2.9%~5.1% and the recoveries of K were between 96.4%~105.4%.