Significantly Enhanced Robustness of K Isotope Analysis by Collision Cell MC-ICP-MS and Its Application to the Returned Lunar Samples by China’s Chang’e-5 Project
Significantly Enhanced Robustness of K Isotope Analysis by Collision Cell MC-ICP-MS and Its Application to the Returned Lunar Samples by China’s Chang’e-5 Project
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碰撞室 MC-ICP-MS 钾同位素分析的稳健性显着增强及其在中国嫦娥五号工程返回月球样品中的应用
DOI：
10.1021/acs.analchem.2c03989
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发表时间：
2023
影响因子：
7.4
通讯作者：
Li Weiqiang
中科院分区：
文献类型：
--
作者：
An Shichao;Chen Jiayang;Boschi Samuele;Li Weiqiang
利用碰撞池多接收器ICP质谱仪（CC-MC-ICP-MS）可以高灵敏度精确测量稳定钾同位素比值，这是一种新兴的研究工具。然而，它已被证明，钾同位素分析的准确性CC-MC-ICP-MS可能会受到严重损害的痕量水平的钙污染物，虽然这种影响的原因仍然知之甚少。在这里，我们报告的影响，钙对钾同位素分析CC-MC-ICP-MS可以显着减少，如果D2，而不是H2（默认气体）被用作反应气体，进入碰撞池。这表明在碰撞池中产生了带正电荷的氢化钙分子。使用D2作为反应气体避免了在K同位素分析期间Ca引起的不准确问题，因为40 CaD+不像40 CaH+那样干扰41 K +;因此，通过CC-MC-ICP-MS进行的K同位素分析的稳健性显著增强。通过对7个地质标准样品的K同位素分析，验证了该方法的有效性，并将其应用于我国嫦娥五号返回样品的亚微克级K消耗，揭示了17 mg月球玄武岩碎片中K同位素的显著变化。
Stable K isotope ratios, an emerging research tool for a wide range of problems, can be measured precisely with high sensitivity by using collision cell multicollector ICP mass spectrometers (CC-MC-ICP-MS). However, it has been shown that the accuracy of K isotope analysis by CC-MC-ICP-MS could be compromised severely by trace-level Ca contaminants, although the cause of such an effect remains poorly understood. Here, we report that the influence of Ca on K isotope analysis by CC-MC-ICP-MS can be dramatically reduced if D2 rather than H2 (the default gas) is used as the reaction gas that goes into the collision cell. This indicates the generation of positively charged calcium-hydride molecules in the collision cell. Usage of D2 as reaction gas circumvents the Ca-induced inaccuracy issues during K isotope analysis because 40CaD+ does not interfere with 41K+ as 40CaH+ does; as such, the robustness of K isotope analysis by CC-MC-ICP-MS is significantly enhanced. This improved method is verified by K isotope analysis of seven geostandards, and applied to China’s Chang’e-5 lunar return samples at submicrogram K consumption, revealing significant K isotope variability within a 17 mg lunar basalt fragment.