Abstract This study presented a chemical protocol for purification of calcium and magnesium from a single aliquot of biological and geological samples. The separation protocol was based on a two-step cation exchange chromatography using DGA resin and AG50W-X12 (200–400 mesh) resin. Calcium fraction was first collected using 0.25 mL of DGA resin, and Mg fraction was then collected using 0.5 mL of AG50W-X12 cation exchange resin. For Ca isotope analysis, the effect of acidity and concentration mismatch as well as the matrix effect were rigorously evaluated using the Neptune Plus MC-ICP-MS with a wet-plasma mode. Based on repeated measurements on BHVO-2 and NIST SRM 1400, the long-term reproducibility was evaluated at 0.08‰ (2SD) for δ44/42Ca915a. The δ26Mg ratios of the analyzed reference materials varied from −1.22‰ to 0.03‰ with the external precision better than 0.11‰ (2SD). The robustness of the protocol has been validated by replicated analyses of biological and geological standards. Calcium and magnesium isotopic ratios of all reference materials measured in this study agreed well with previous data within uncertainties. Therefore, the proposed method can be used for simultaneous determination of Ca and Mg isotopic ratios from a single aliquot of biological and geological samples.

中文翻译：

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用 MC-ICP-MS 色谱纯化生物和地质样品中的 Ca 和 Mg 以进行同位素分析

摘要 本研究提出了一种从生物和地质样品的单等分试样中纯化钙和镁的化学方案。分离方案基于使用 DGA 树脂和 AG50W-X12（200-400 目）树脂的两步阳离子交换色谱法。首先使用 0.25 mL DGA 树脂收集钙部分，然后使用 0.5 mL AG50W-X12 阳离子交换树脂收集 Mg 部分。对于 Ca 同位素分析，使用湿等离子体模式的 Neptune Plus MC-ICP-MS 严格评估酸度和浓度不匹配的影响以及基质效应。基于对 BHVO-2 和 NIST SRM 1400 的重复测量，δ44/42Ca915a 的长期重现性评估为 0.08‰ (2SD)。分析的参考材料的 δ26Mg 比率从 -1.22‰ 到 0 不等。03‰，外部精度优于0.11‰（2SD）。该协议的稳健性已通过生物和地质标准的重复分析得到验证。本研究中测量的所有参考材料的钙镁同位素比率与之前的数据非常吻合，但存在不确定性。因此，所提出的方法可用于同时测定生物和地质样品的单等分试样中的 Ca 和 Mg 同位素比率。