Efficient Acid Leaching of Geological Samples for Lead Isotope Analysis
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摘要: 针对地质样品的Pb同位素分析提出了一种简化淋洗法, 以去除样品碎样过程引起的污染.相对前人的淋洗法而言, 简化淋洗法不仅能够得到地质样品中准确的Pb同位素组成, 而且降低了全流程本底并提高了样品处理效率.利用多接收等离子体质谱分析了5个美国地质调查局(USGS) 国际标准参考物质(AGV-1、AGV-2、BHVO-2、BCR-2和G-2) 中的Pb同位素组成, 结合前人的研究, 结果表明第一、二代USGS参考物质在制样过程中均受到不同程度的污染.第一代标准在碎样过程受到的污染比碎样环境造成的普通铅污染严重, 而第二代则相反.淋洗后各种参考物质分别具有相近且均一的Pb同位素组成, 表明对岩石粉末样进行溶样前的淋洗有助于获得样品真实的Pb同位素组成.Abstract: We present a simplified acid leaching method for lead isotope analysis of geological samples using multiple-collector inductively-coupled-plasma mass-spectrometry (MC-ICP-MS), to remove any contamination during sample preparation. The method is featured with higher throughput, and lower lead background using one step of weak hydrochloric acid leaching. Lead isotopic compositions of five United States Geological Survey (USGS) reference materials (AGV-1, AGV-2, BHVO-2, BCR-2, and G-2) were measured. The results show that both generations of USGS standards were contaminated during sample preparation. The grinding procedure and crushing environment were the dominating sources of contamination for the first and the second generations, respectively. The homogeneous lead isotopic compositions of these standards demonstrate that the one-step weak acid leaching is efficient and necessary for obtaining reliable lead isotope compositions in geological samples.
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Key words:
- lead isotope /
- leaching /
- USGS reference material /
- multiple collector ICP-MS
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图 1 淋洗实验对第一代(AGV-1、BCR-1、BHVO-1) 和第二代(AGV-2、BCR-2、BHVO-2) USGS标准参考物质中Pb同位素组成的影响
实心标记为第一代标准参考物质, 空心标记为第二代标准参考物质.圆形、菱形和三角形分别表示未淋洗样品、淋洗后的残渣和样品淋洗后的淋洗液.黑色点为本文数据; 灰色点数据引自Weis et al. (2005, 2006).图中误差为2σ, 未标误差范围的分析点表明实际误差小于相应的分析点
Fig. 1. Effect of the leaching experiments on lead isotopic compositions of two generations of USGS reference materials
图 2 不同淋洗方法分析AGV-1、AGV-2、BCR-2、BHVO-2中Pb同位素结果
三角、方块和圆分别表示样品淋洗采用WF、MC和本文的简化法
Fig. 2. Pb isotopic compositions of residues of AGV-1, AGV-2, BCR-2, BHVO-2 with different leaching procedures
图 3 不同淋洗方案淋洗USGS参考物质的回收率
A, B和C分别代表WF、MC和本文的简化法
Fig. 3. Recovery of the USGS reference materials after different leaching methods
图 4 不同淋洗方法分析G-2中Pb同位素结果
A, B和C分别代表WF、MC和本文的简化法.液渣表示淋洗液中的残渣; (c), (d) 分别表示(a), (b) 中方框部分
Fig. 4. Pb isotopic compositions of residues of G-2 with different leaching procedures
表 1 3种代表性的淋洗流程对比
Table 1. Comparison of three stepwise leaching schemes for lead separation
表 2 地质样品中Pb分离化学流程
Table 2. Chemical procedure for lead separation of geological samples
表 3 采用不同淋洗方法分析7种标准参考物质的Pb同位素组成
Table 3. Pb isotopic compositions of seven USGS reference materials using different leaching methods
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