Improving Peak Capacity in Glycan Ion Mobility Separations through Traveling Wave-Based Ion Heating.

Complex carbohydrates, such as N-linked glycans, are highly important biomolecules with roles ranging from signaling to recognition and immune response. Ion mobility spectrometry-mass spectrometry (IMS-MS) has emerged as a rapid and orthogonal analytical technique to condensed-phase separations for studying carbohydrates, but many challenges exist in their analyses with IMS-MS due to their isomeric and conformational heterogeneity. Specifically, glycan IMS-MS separations often display more peaks than what can be predicted based on structure and/or much broader than expected peaks presumably from their metal-adducted conformers. This has precluded IMS-MS from being routinely used to analyze complex glycans largely because of the reduction in overall peak capacity and thus difficulty in deconvolving mixtures. In this work, we present a traveling wave-based ion heating strategy that uses activating traveling wave conditions. We demonstrated that this ion heating approach can improve peak capacity for individual glycan species as well as for those in mixtures. Importantly, we did not observe any significant loss in sensitivity and comparable resolution to glycans analyzed at gentle traveling wave conditions. Additionally, we demonstrated that isomeric glycans could be repeatedly cycled resulting in scalable resolution without significant ion losses. Overall, our approach can be broadly implemented on any traveling wave-based IMS-MS platform, and we envision utility toward other molecular classes desiring improved IMS-MS peak capacities.