Characterization of the glycosidic linkage of underivatized disaccharides by interaction with Pb(2+) ions.

Electrospray ionization in combination with tandem mass spectrometry and lead cationization is used to characterize the linkage position of underivatized disaccharides. Lead(II) ions react mainly with disaccharides by proton abstraction to generate [Pb(disaccharide)(m)-H](+) ions (m = 1-2). At low cone voltages, an intense series of doubly charged ions of general formula [Pb(disaccharide)(n)](2+) are also observed.