电感耦合等离子体质谱法测定高纯五氧化二铌中25种痕量杂质元素

采用电感耦合等离子体质谱法(ICP-MS)测定高纯五氧化二铌中痕量Mg、K、Ca、Cr、Fe时,因质谱干扰严重,从而导致其背景等效浓度值(BEC)较高进而无法准确测定。实验采用氢氟酸-硝酸体系以微波消解方式消解样品,以标准加入法补偿基体效应,控制基体质量浓度为500μg/mL,建立了ICP-MS测定高纯五氧化二铌中包括Mg、K、Ca、Cr、Fe在内的25种痕量杂质元素的分析方法。研究表明:采用屏蔽矩冷等离子体技术,在500μg/mL的五氧化二铌基体溶液中,Na、Mg、Al、K、Ca、Cr、Fe、Cu、Co、Ni、Mn的BEC得到明显改善,尤其是Mg、K、Ca、Cr、Fe的BEC改善效果最为显著,由常规模式下的56.5~194ng/mL降至冷等离子体模式下的0.012~0.203ng/mL;使用经实验室亚沸蒸馏提纯的电子级氢氟酸及硝酸可有效地降低试剂空白值。各元素校准曲线线性相关系数均大于0.9990;方法中各元素的检出限在0.001~0.010μg/g之间,测定下限在0.003~0.033μg/g之间。采用实验方法对高纯五氧化二铌样品中25种杂质元素进行测定,结果表明,各元素测定结果的相对标准偏差(RSD,n=11)为0.90%~12.7%,回收率为91%~111%。方法应用于两批纯度为99.999%的超高纯五氧化二铌实际样品分析,结果与辉光放电质谱法(GD-MS)基本一致。

Determination of twenty-five trace impurity elements in high purity niobium pentoxide by inductively coupled plasma mass spectrometry

During the determination of trace Mg, K, Ca, Cr and Fe in high purity niobium pentoxide by inductively coupled plasma mass spectrometry (ICP-MS), these impurity elements could not be accurately determined due to the high background equivalent concentrations (BECs) which were caused by the serious mass spectral interferences. After the sample was treated by microwave digestion with HF-HNO₃ system and the matrix effect was corrected by the standard addition method, an analysis method of 25 trace impurity elements (including Mg, K, Ca, Cr, Fe, etc) in high-purity niobium pentoxide by ICP-MS was established with matrix mass concentration at 500μg/mL. The results indicated that BECs of Na, Mg, Al, K, Ca, Cr, Fe, Cu, Co, Ni and Mn were obviously improved in 500μg/mL niobium pentoxide matrix solution by the shield torch cool plasma technology. Particularly, the improvement effect of BECs of Mg, K, Ca, Cr and Fe were the most significant, which were reduced from 56.5-194ng/mL at normal mode to 0.012-0.203ng/mL at cool plasma mode. The reagent blank could be effectively reduced by the electronic-grade HF and HNO₃ purified in laboratory by sub boiling distillation. The linear correlation coefficients of calibration curves of elements were all higher than 0.9990. The detection limits of elements in this method were in the range of 0.001-0.010μg/g, and the low limits of determination were between 0.003μg/g and 0.033μg/g. The contents of 25 impurity elements in high purity niobium pentoxide sample were determined according to the experimental method. The results showed that the relative standard deviations of determination results (RSD, n=11) were between 0.9% and 12.7%, and the spiked recoveries were between 91% and 111%. The proposed method was applied for the analysis of two batches of actual ultra-pure niobium pentoxide samples (the purity was 99.999%). The results were basically consistent with those obtained by GD-MS.