Cyclic IMS-MS evidence for potential ring opening in collisionally activated sodiated cyclodextrins

Current tandem mass spectrometry-based methods for cyclodextrin characterization rely on exact mass and fragmentation patterns. Orthogonal methods are designed to provide additional information, increasing confidence in characterization. Ion mobility spectrometry (IMS) and mass spectrometry (MS) provide two dimensions where MS separates based on mass-to-charge and IMS separates based on size, shape, and charge. Here, we report new gas phase behavior of sodiated cyclodextrins revealed by cyclic IMS coupled to tandem MS. Gas phase ion activation prior to IMS separation on sodiated α-, β-, and γ-cyclodextrins generates isomeric species with different mobilities. Following gas phase mobility separation, fragmentation studies on the activation-generated isomers showed a greater degree of fragmentation than was observed for the original sodiated cyclodextrins. These findings suggest that sodiated cyclodextrins undergo structural changes upon activation, with the newly formed isomers significantly contributing to the observed fragmentation. To our knowledge this is the first report on separation of isomeric ions generated upon collisional activation of sodiated cyclodextrins in the gas phase. The results of this study can be used for better understanding of cyclodextrin fragmentation, suggesting that fragmentation occurs after an initial isomerization, possibly to a ring-opened form. Additionally, these findings can be used to develop more specific methodologies for cyclodextrin characterization.