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.

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 D