Isotopic Effect on Ion Mobility and Separation of Isotopomers by High-Field Ion Mobility Spectrometry

摘要

Distinguishing and separating isotopic molecular variantsnis important across many scientific fields. However,ndiscerning such variants, especially those producing nonnet mass difference, has been challenging. For example,nsingle-stage mass spectrometry is broadly employed tonanalyze isotopes but is blind to isotopic isomers (isotopomers)nand, except at very high resolution, species ofnthe same nominal mass (isobars). Here, we report separationnof isotopic ions, including isotopomers and isobars,nusing ion mobility spectrometry (IMS), specifically, thenfield asymmetric waveform IMS (FAIMS). The effect is notnbased on the different reduced masses of ion-gas moleculenpairs previously theorized to cause isotopic separationsnin conventional IMS, but appears related to thendetails of energetic ion-molecule collisions in strongnelectric fields. The observed separation qualitatively dependsnon the gas composition and may be improved usingngas mixtures. Isotopic shifts depend on the position ofnthe labeled site, which allows its localization and containsninformation about the ion geometry, potentially enablingna new approach to molecular structure characterization.