Structural analysis of oligosaccharides by tandem mass spectrometry: Collisional activation of sodium adduct ions

The collisionally activated dissociation (CAD) spectra of the sodium adduct ions of several oligosaccharides were obtained and compared to CAD spectra of the protonated molecules. Isomeric lacto‐N‐fucopentose I and lacto‐N‐fucopentose II, stachyose and maltodecaose are discussed here. Both natriated and protonated molecules provide familiar oxonium ion series through bond scissions in the glycosidic linkages under 8 keV collisions with helium. Natriated adducts also undergo two‐bond cross‐ring cleavages analogous to those observed in the laser desorption mass spectra of oligosaccharides. The relative contributions of glycosidic and cross‐ring ion series in the CAD spectra of sodium adducts of carbohydrates are dependent on and can be controlled by collision energies in the 1‐8 keV range.