In this study, we develop a method for high precision Cd isotope analysis by double spike MC-ICP-MS. Two-step Cd purification using AG-MP-1M resin and TRU resin was used to separate Cd from samples with a recovery of more than 95% Cd and a blank less than 0.1 ng. A practical double spike design and optimization procedure is proposed and the effect of the double spike ratio in the double spike-sample mixture (p) on the measured δ^114/110Cd is evaluated, which broadens the appropriate p range from 0.3–0.6 to 0.1–0.8. In addition, the observed shift/deviation of the measured δ^114/110Cd_{NIST 3108} value from zero-delta due to the change of experimental conditions is discussed on a theoretical basis and a correction approach is developed. Potential Mo and Zr based polyatomic ions have no significant effect on δ^114/110Cd in typical geological samples, while isobaric ions such as Sn, Pd and In can seriously affect the accuracy of measurements even at low concentration. It is shown that the tolerances of isobaric interference can be improved to 0.1, 0.05 and 0.02 for Sn/Cd, Pd/Cd and In/Cd, respectively, after mass discrimination correction. The precision and accuracy of the proposed method were verified by analyzing mixtures of NIST 3108 and a secondary reference material BGEG-Cd of different composition. Long term monitoring of the measured NIST 3108 and BGEG-Cd showed repeatability for δ^114/110Cd of 0.00 ± 0.04‰ and −1.00 ± 0.04‰ (2sd, n = 45), respectively. Finally, we measured Cd isotope compositions of several geological standard materials including soil sediments and manganese nodules, and the δ^114/110Cd values of 0.01 ± 0.02‰ (GSD-5a), 0.04 ± 0.02‰ (GSD-7a), −0.06 ± 0.05‰ (GSD-10), −0.34 ± 0.06‰ (GSD-11), −0.10 ± 0.06‰ (GSD-12), 0.10 ± 0.04‰ (GSD-17), 0.05 ± 0.03‰ (GSD-21), and 0.10 ± 0.07‰ (GSD-23) were in good agreement with the reported values, and a δ^114/110Cd value of −0.08 ± 0.04‰ (GSD-3a) was reported for the first time.

中文翻译：

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双峰MC-ICP-MS对地质参考物质进行高精度镉同位素分析

在这项研究中，我们开发了一种通过双峰MC-ICP-MS进行高精度Cd同位素分析的方法。使用AG-MP-1M树脂和TRU树脂进行的两步Cd纯化可从样品中分离Cd，回收率大于95％Cd，空白量小于0.1 ng。一种实用的双穗设计和优化过程，提出并在双尖峰样品混合物（双穗比的效果p）上测得的δ ^110分之114镉被评估，从而拓宽适当p范围从0.3-0.6至0.1–0.8。此外，所测量的被观察者移位/偏差δ ^110分之114镉_{NIST 3108}从理论上讨论了由于实验条件的变化而导致的零增量值的变化，并提出了一种校正方法。潜在Mo和Zr基的多原子离子对没有显著效果δ ^110分之114典型地质样品中的镉，而同量异位的离子如Sn，Pd和在即使在低浓度严重影响测量的准确性。结果表明，质量歧视校正后，Sn / Cd，Pd / Cd和In / Cd的等压干扰容限分别提高到0.1、0.05和0.02。通过分析NIST 3108和成分不同的次要参考材料BGEG-Cd的混合物，验证了该方法的准确性和准确性。长期监测测得的NIST 3108和BGEG-Cd显示了δ ^110分之114的0.00±0.04‰和-1.00±0.04‰（2SD，镉Ñ分别= 45）。最后，我们测量的几个地质标准材料包括土壤沉积物和锰结核镉同位素组合物和δ ^110分之114的CD值0.01±0.02‰（GSD-5A），0.04±0.02‰（GSD-7A）， - 0.06 ±0.05‰（GSD-10），-0.34±0.06‰（GSD-11），-0.10±0.06‰（GSD-12），0.10±0.04‰（GSD-17），0.05±0.03‰（GSD-21）和0.10±0.07‰（GSD-23）是与报道的值一致，以及δ ^110分之114报道首次-0.08±0.04‰（GSD-3a）的Cd值。