Mass spectrometric decompositions of cationized β-cyclodextrin

The mass spectrometric decompositions of β-cyclodextrin (β-CD) complexed with a number of common divalent metal cations (Mg, Ca, Cd, Cu, Co and Pb), obtained under electrospray ionization conditions, are reported. The main fragmentation pathways of [β-CD + Cat]2+ ions studied (Cat stands for divalent cation) consist of consecutive losses of sugar units. The rupture of C–C bond in sugar units, which occurs via hydrogen atom transfer from the fragment ion formed to the eliminated species, was also observed. Isotope labelling consisting of the exchange of all hydroxyl hydrogens for deuteriums, has been applied in order to understand better the formation of fragment ions. It was found that C–H hydrogen transfer proceeds only during fragmentation across C–C bonds.