Charge Inversion Ion/Ion Reactions Coupled to Ion Mobility/Mass Spectrometry: Oligosaccharides

Various ion mobility-basedseparation techniques andinstrumentshave been recently developed to increase the operational resolutionof ion mobility separations, especially of isomers and isobars. Inaddition to developments in instrumentation, different covalent andnoncovalent derivatization techniques have helped achieve effectiveseparations by magnifying minor differences in collision cross section.Among these methodologies is host-guest complex formation and,a new development presented herein, charge inversion ion-ionreactions coupled to ion mobility separations. We used these methodsto enable formation of complexes between isomeric deprotonated oligosaccharidesand alkaline earth metals (in solution) and alkaline earth metal-trisphenanthrolinecomplexes (in vacuo), observing minor shifts in ion mobility arrivaltimes for the charge inversion reaction products as well as uniquemobility fingerprints indicative of separations of alpha/beta anomers of disaccharides. For example, we have demonstrated separationsbetween reducing disaccharides such as lactose and lactulose and nonreducingdisaccharides. We also observed separations based on the pyranose/furanoseconfigurations of the isomers. These results suggest the potentialfor ion/ion reactions to enable isomer separation of biomoleculesfrom various compound classes using ion mobility-mass spectrometry(IM-MS).