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-betaCD (Glc1-betaCD) and maltosyl-alphaCD (Glc2-alphaCD) 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 CD 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-micros) of the product ions [M-Glc(n) + H]+ (n = 0-6) 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(2-6) + H]+ of Glc1-betaCD and [M-Glc(3-6) + H]+ of Glc2-alphaCD product ions' plots were on the same trend line as gamma-CD. The plots of [M-Glc1 + H]+ of Glc1-betaCD and [M-Glc(1, 2) + H]+ of Glc2-alphaCD 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 Glc1-beta CD and Glc2-alphaCD retained their CD structure. Analyses of the IM peak widths enable us to elucidate the structures of the product ions.