COLLISION-INDUCED DISSOCIATION OF GLYCOSIDE ALKALI-METAL ADDUCT IONS IN FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

The collision-induced dissociation (CID) spectra of glycoside-alkali m etal adduct ions [M + C]+ (C = Li, Na, K and Rb) produced under fast a tom bombardment (FAB) conditions are reported. The results obtained su ggested that the CID spectra of the [M + C]+ ions of some flavonoid gl ycosides reflect the coordination structures because the CID patterns generally changed with the metal cation size. In diglycosides, the CID spectra showed that the relatively small cations Li+ and Na+ rather b ind to the sugar moiety, whereas the large cations K+ and Rb+ rather b ind to the aglycone moiety. In monoglycosides, the cations C+ rather b ind to the aglycone moiety. It was concluded that the CID technique co mbined with FAB is useful for the structural elucidation of [M + C]+ i ons and, in principle, the CID spectra reflect the coordination struct ures in the gas phase.