Carbohydrate isomer resolution via multi-site derivatization cyclic ion mobility-mass spectrometry

Oligosaccharides serve many roles in extant life and may have had a significant role in prebiotic chemistry on the early Earth. In both these contexts, the structural and isomeric diversity among carbohydrates presents analytical challenges necessitating improved separations. Here, we showcase a chemical derivatization approach, where 3-carboxy-5-nitrophenylboronic acid (3C5NBA) is used to label vicinal hydroxyl groups, amplifying the structural difference between isomers. We explore the applicability of state-of-the-art ion mobility - mass spectrometry (IM-MS) instrumentation in the analysis of derivatized carbohydrates. In particular we focus on the resolving power required for IM separation of derivatized isomers. A recently developed cyclic ion mobility (cIM) mass spectrometer (MS) was chosen for this study as it allows for multi-pass IM separations, with variable resolving power (Rp). Three passes around the cIM (Rp ∼ 120) enabled separation of all possible pairs of four monosaccharide standards, and all but two pairs of eight disaccharide standards. Combining cIM methodology with tandem mass spectrometry (MS/MS) experiments allowed for the major products of each of the 3C5NBA carbohydrate derivatization reactions to be resolved and unequivocally identified.