Accurate Determination of Trace Gallium in Geological Samples by Inductively Coupled Plasma-Mass Spectrometry
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摘要: 应用电感耦合等离子体质谱法(ICP-MS)对地质样品中微量元素镓进行测试分析时,存在两方面问题:一是不同消解方法各有不足,密闭式消解不能批量处理样品,而敞开式消解过程繁杂;二是质谱测试时需要选择69Ga还是71Ga,确定扣除哪些干扰和相应的扣除系数,这些因素使地质样品中镓元素的测试精度不高。本文基于一般地质样品中有机质含量低的特点,针对ICP-MS分析方法提出:①使用氢氟酸、盐酸、硝酸、高氯酸四种酸混合消解样品,采用半密闭式酸分解法,通过调整加热温度、用酸量、用酸比等加快反应进程,少量的有机质在强酸加热消解时能够反应完全,而不必要进行灰化处理;②采用丰度为39.9%的71Ga进行测试,使用经验系数0.005,利用55Mn18O对71Ga位置扣除55Mn16O的干扰。方法精密度在3%以内,方法检出限为0.06 μg/g。本方法简化了样品消解过程,并可批量处理样品,降低了分析成本,在准确测定镓元素的同时还能理想地测定其他微量元素和稀土元素。
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关键词:
- 地质样品 /
- 镓 /
- 电感耦合等离子体质谱法 /
- 矿物消解
Abstract: There are two problems in the quantitative analysis of trace gallium in geological samples by using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Firstly, the usual advantages of having two kinds of digestion methods are irrelevant here because sealed digestion is not appropriate for batch processing samples and an open-system digestion process is a complex procedure. Secondly, the selection of 69Ga or 71Ga and the related interference correction are the main factors leading to low precision. The method based on the characteristic of low content organic matter in normal geology samples and requirements for ICP-MS measurement is improved on and discussed. The four-acid digestion system of HF-HCl-HNO3-HClO4 was conducted to dissolve the samples in a semi-hermetic environment. Adjustment of the heating temperature, acid amounts and ratios can speed up the reaction. The samples with low content organic matter are digested completely in the strong acids solution without ashing. 71Ga with an abundance of 39.9% and an empirical coefficient of 0.005 was selected. The interference of 55Mn16O interference on the 71Ga peak was corrected by 55Mn18O. The accuracy and precision of gallium is within 3%, and the detection limit is 0.06 μg/g. The improved method simplifies the chemical procedure and reduces the cost which is advantageous for batch processing. Moreover, this method is also suitable for other trace elements and rare earth elements. -
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表 1 仪器工作条件
Table 1. Working parameters of the ICP-MS instrument
工作参数 设定条件 射频功率 1150 W 采样深度 112 mm 采样锥直径 1.0 mm 截取锥直径 0.7 mm 辅助气流量 0.85 L/min 冷却气流量 13.2 L/min 雾化气流量 0.75 L/min 检测器模式 双模 每个质量通道数 3 扫描次数 60 表 2 样品灰化处理的比较
Table 2. Comparison of sample drying pretreatment
标准物质编号 样品处理方法 w/(μg·g-1) 相对误差
RE/%RSD/% 标准值 测量值 GBW
07404
(土壤)未灰化+敞开式消解 31±3 29.9 3.55 5.6 300℃灰化+敞开式消解 31±3 29.5 4.84 6.0 500℃灰化+敞开式消解 31±3 29.4 5.16 7.4 700℃灰化+敞开式消解 31±3 28.6 7.74 10.3 GBW
07424
(土壤)未灰化+敞开式消解 18±1 17.5 2.78 3.9 300℃灰化+敞开式消解 18±1 17.2 4.44 6.2 500℃灰化+敞开式消解 18±1 17.1 5.00 7.7 700℃灰化+敞开式消解 18±1 16.9 6.11 9.4 表 3 样品消解方法的比较
Table 3. Comparison of sample digestion methods
标准物质编号 样品消解方法 w/(μg·g-1) 相对误差
RE/%RSD/% 标准值 测量值 GBW
07401敞开式酸分解法 19.3±1.1 17.8 7.77 7.3 密闭式微波消解法 19.3±1.1 18.9 2.07 2.1 半密闭式酸分解法 19.3±1.1 18.8 2.64 3.1 GBW
07430敞开式酸分解法 25.1±1.2 23.5 6.37 5.6 密闭式微波消解法 25.1±1.2 24.7 1.55 2.0 半密闭式酸分解法 25.1±1.2 24.5 2.43 2.6 表 4 方法准确度和精密度
Table 4. Accuracy and precision tests of the method
标准物质编号 同位素 w/(μg·g-1) 相对误差
RE/%RSD/% 标准值 实测值 GBW 07402 69Ga 12±1 11.2 7.08 7.83 GBW 07407 69Ga 39±5 37.1 4.90 5.42 GBW 07402 71Ga 12±1 11.7 2.83 3.64 GBW 07407 71Ga 39±5 38.3 1.77 2.09 表 5 方法准确度和精密度
Table 5. Accuracy and precision tests of the method
元素 w/(μg·g-1) 相对误差
RE/%RSD/% 标准值 测定值 Li 55±2 54.8 0.36 1.3 Be 1.85±0.34 1.82 1.62 3.2 Sc 20±2 21.1 5.5 4.6 Co 22±2 21.9 0.45 3.0 Ni 64±5 65.2 1.88 3.2 Cu 40±3 42.2 5.5 3.7 Rb 75±4 76.2 1.6 1.2 Sr 77±6 76.7 0.39 1.1 Mo 2.6±0.3 2.56 1.54 4.2 Sb 6.3±1.1 6.28 0.32 2.9 Cs 21.4±1.0 20.9 2.34 1.0 Ba 213±20 213.2 0.09 0.8 La 53±4 53.2 0.38 1.3 Ce 136±11 131 3.68 1.4 W 6.2±0.5 5.90 4.84 2.1 Tl 0.94±0.25 0.93 1.06 3.8 Pb 58±5 56.7 2.24 1.6 Bi 1.04±0.13 1.01 2.88 3.0 Th 27±2 28 3.70 4.2 U 6.7±0.8 6.9 2.99 2.3 -
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