Peak width-mass correlation in CID MS/MS of isomeric oligosaccharides using traveling-wave ion mobility mass spectrometry

Isomeric oligosaccharides gamma-cyclodextrin (gamma-CD), glucosyl-beta CD (Glc(1)-beta CD) and maltosyl-alpha CD (Glc(2)-alpha CD) were analyzed by traveling-wave ion mobility (twIM) mass spectrometry (MS). Their formation of multicharged multimers differed from each other. The ion mobility-mass spectrometry was useful in the self-assembling and complex formation analyses of CID isomers. The drift times of the isomers and their product ions with the same mass were almost the same in collision-induced dissociation (CID) MS/MS. In contrast, the ion mobility peak widths were sensitive to structural differences of the isomeric product ions. The twIM peak width (ms - mu s) of the product ions [M - Glc(n) + H](+) (n = 0 similar to 6) of gamma-CD correlated linearly with their masses (Da); the large and/or long chain product ions had wider peak widths, which were much wider than those from the general diffusion effect. This was a novel and useful 'trend line' to discriminate between the three isomers. Plots of [M - Glc(2 similar to 6) + H](+) of Glc(1)-beta CD and [M - Glc(3 similar to 6) + H](+) of Glc(2)-alpha CD product ions' plots were on the same trend line as gamma-CD. The plots of [M - Glc(1) + H](+) of Glc(1)-beta CD and [M - Glc(1,2) + H](+) of Glc(2)-alpha CD strayed from the gamma-CD line; their peak widths were narrower than those of gamma-CD. These results indicated that product ions from the chemical species of Glc(1)-beta CD and Glc(2)-alpha CD retained their CD structure. Analyses of the IM peak widths enable us to elucidate the structures of the product ions. Copyright (C) 2009 John Wiley & Sons, Ltd.