Schaefer Christoph, Kirk Ansgar T, Allers Maria, Zimmermann Stefan
Institute of Electrical Engineering and Measurement Technology, Department of Sensors and Measurement Technology, Leibniz University Hannover, Appelstr. 9A, 30167 Hannover, Germany.
J Am Soc Mass Spectrom. 2020 Oct 7;31(10):2093-2101. doi: 10.1021/jasms.0c00220. Epub 2020 Sep 16.
Ion mobility spectrometers (IMS) separate ions mainly by ion-neutral collision cross section and to a lesser extent by ion mass and effective temperature. When investigating isotopologues, the difference in collision cross section can be assumed negligible. Since the mobility shift of isotopologues is thus mainly caused by their difference in mass and effective temperature, the investigation of isotopologues can provide important insights into the theory of ion mobility. However, in classical IMS operated at ambient pressure, cluster formation with neutral molecules occurs, which significantly influences the mobility shift of isotopologues and thus makes a sound investigation of the effect of ion mass and effective temperature on the ion mobility difficult. In this work, the relative ion mobility of several organic compounds and their C-labeled isotopologues is studied in a High Kinetic Energy Ion Mobility Spectrometer (HiKE-IMS) at high reduced electric fields up to 120 Td, which allows the investigation of nonclustered ion species and thus enables a sound investigation of the mobility shift of isotopologues. The results show that the measured relative ion mobilities of isotopologues having the same effective temperature and, thus, their ion mass dominating the relative ion mobility agree well with theoretical relative ion mobilities predicted by the theory of ion mobility.
离子迁移谱仪（IMS）主要通过离子与中性粒子的碰撞截面来分离离子，在较小程度上还通过离子质量和有效温度来分离。在研究同位素异构体时，可以认为碰撞截面的差异可忽略不计。由于同位素异构体的迁移率变化主要由其质量和有效温度的差异引起，因此对同位素异构体的研究可为离子迁移理论提供重要见解。然而，在常压下运行的传统IMS中，会发生与中性分子的团簇形成，这会显著影响同位素异构体的迁移率变化，从而难以对离子质量和有效温度对离子迁移的影响进行可靠研究。在这项工作中，在高达120 Td的高折合电场下，在高动能离子迁移谱仪（HiKE-IMS）中研究了几种有机化合物及其碳标记的同位素异构体的相对离子迁移率，这使得能够研究非团簇离子物种，从而能够可靠地研究同位素异构体的迁移率变化。结果表明，具有相同有效温度、因而其离子质量主导相对离子迁移率的同位素异构体的实测相对离子迁移率，与离子迁移理论预测的理论相对离子迁移率吻合良好。
