Separation of isomers using a differential mobility analyser (DMA): Comparison of experimental vs modelled ion mobility

Mass spectrometry is uniquely suited to identify and quantify environmentally relevant molecules and molecular clusters. Mass spectrometry alone is, however, not able to distinguish between isomers. In this study, we demonstrate the use of both an experimental set-up using a differential mobility analyser, and computational ion mobility calculations for identification of isomers. In the experimental set-up, we combined electrospray ionisation with a differential mobility analyser time-of-flight mass spectrometer to separate environmentally relevant constitutional isomers, such as catechol, resorcinol and hydroquinone, and configurational isomers, such as cyclohexanediols and fatty acids (i.e., oleic and elaidic acids). Computational ion mobility predictions were obtained using the Ion Mobility Software (IMoS) program. We find that isomer separation can be achieved with the differential mobility analyser, while for catechol, resorcinol and hydroquinone, the computational predictions can reproduce the experimental order of the ion mobilities between the isomers, confirming the isomer identification. Our experimental set-up allows analysis both in the gas and liquid phase. The differential mobility analyser can, moreover, be combined with any mass spectrometry set-up, making it a versatile tool for the separation of isomers.