Separation of Mg, Ca and Fe from geological reference materials for stable isotope ratio analyses by MC-ICP-MS and double-spike TIMS
Separation of Mg, Ca and Fe from geological reference materials for stable isotope ratio analyses by MC-ICP-MS and double-spike TIMS
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DOI：
10.1039/b820154d
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发表时间：
2009-04
影响因子：
3.4
通讯作者：
F. Wombacher;A. Eisenhauer;A. Heuser;S. Weyer
中科院分区：
文献类型：
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作者：
F. Wombacher;A. Eisenhauer;A. Heuser;S. Weyer
通常需要从样品基质中近定量分离分析物元素以获得精确和准确的稳定同位素数据，特别是如果MC-ICP-MS与标准样品交叉（SSB）技术结合使用以进行质量偏差漂移校正。在这里，我们报告了一个强大的程序，允许联合化学分离镁，钙和铁，使用离子交换柱，含有1毫升AG 50 W-X8（200-400目）阳离子交换树脂。镁从许多地质样品类型中分离出来，用于同位素比分析，只需通过该柱一次。对于Mg纯化，使用稀HF和丙酮-HCl混合物选择性洗脱Be、Ti、Mn、Fe和Al。从Ca为主的碳酸盐样品中分离Mg和/或从相同样品等分试样中分离Mg、Ca和Fe的组合是通过将Ca和Fe从10 M HCl吸附到离子交换树脂上来实现的。在提纯之后，用MC-ICP-MS（Mg和Fe同位素）和双尖峰TIMS（Ca同位素）分析了地质参考材料，包括水、骨骼、碳酸盐和沉积物样品、火成岩和沉积岩以及一颗南极陨石。26 Mg/24 Mg、44 Ca/40 Ca和56 Fe/54 Fe的平均外部重复性分别为±0.16‰、±0.26‰和±0.05‰（2sd; n ≥ 5）。与已发布数据的比较证明了结果的准确性。对于使用SSB-MC-ICP-MS的Mg同位素分析，使用元素添加研究了基质诱导的质量偏差效应。人工基质在随后的标准分析中留下了记忆，这可能是由于锥体上的沉积物。该观察结果允许检测未知样品中的基质效应。最后，简要讨论了镁和钙零δ标准物质的现状。
Near quantitative separation of analyte elements from the sample matrix is commonly required to obtain precise and accurate stable isotope data, especially if MC-ICP-MS is used in conjunction with the standard-sample bracketing (SSB) technique for mass bias drift correction. Here, we report a robust procedure that allows for the combined chemical separation of Mg, Ca and Fe, using ion-exchange columns that contain 1 ml AG50W-X8 (200–400 mesh) cation exchange resin. Magnesium was separated for isotope ratio analyses from many geological sample types by a single pass through this column. For Mg purification, Be, Ti, Mn, Fe and Al are selectively eluted using dilute HF and an acetone–HCl mixture. The separation of Mg from Ca-dominated carbonate samples and/or a combination of Mg, Ca and Fe separation from the same sample aliquot, is achieved by the adsorption of Ca and Fe onto the ion-exchange resin from 10 M HCl. Following purification, geological reference materials, including water, bone, carbonate and sediment samples, igneous and sedimentary rocks and a chondritic meteorite were analysed by MC-ICP-MS (Mg and Fe isotopes) and double-spike TIMS (Ca isotopes). Average external repeatabilities were ±0.16‰ for 26Mg/24Mg, ±0.26‰ for 44Ca/40Ca and ±0.05‰ for 56Fe/54Fe (2sd; n ≥ 5). Comparison with published data documents the accuracy of the results. For Mg isotope analyses using SSB-MC-ICP-MS, matrix-induced mass bias effects were studied using element additions. The artificial matrices left a memory in subsequent standard analyses, likely due to depositions on the cones. This observation allowed for the detection of matrix effects in unknown samples. Finally, the current status of Mg and Ca zero-delta reference materials is briefly discussed.