Efficient Separation of Disaccharide Isomers Using Ion Mobility Spectrometry by Metal Cation and Anion Assisted Strategy

Abstract The rapid separation and identification of disaccharide isomers pose a significant analytical challenge in fields such as food science and glycobiology. This study developed a fast, simple, and low-cost analytical method based on electrospray ionization ion mobility spectrometry (ESI-IMS) combined with an ion adduction strategy for the efficient separation of eight common disaccharide isomers. The principle involves introducing specific metal cations or anions into the disaccharide solution to form stable adducts, thereby significantly altering their drift behavior during IMS analysis. Systematic screening of seven cations and nine anions and mass spectrometry result revealed that in positive ion mode, Cu+ forms structurally rigid dimeric adducts [Cu + 2M]+ with disaccharides, effectively amplifying subtle stereostructural differences into significant distinctions in collision cross section (CCS) and increasing the proportion of fully separated disaccharide pairs to 71.4%. In negative ion mode, I− forms predominantly single [I + M]− adducts, substantially simplifying the complex original spectra and achieving a full separation rate of 60.7%. Theoretical calculations indicated stable electronic structures within the complex systems and the differences in both the strength and interaction characteristics between the two types of adducts. This method requires no complex pretreatment or expensive advanced instrumentation, and is readily implementable on conventional drift-tube IMS platforms. It thus offers a robust, cost-effective, and high-throughput solution for disaccharide isomer analysis, with potential applications in food science, biomedicine, and materials characterization.