ABSTRACT
Oligosaccharide isomers were distinguished by electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry ( ECD-FT-ICR-MS ) in combination with utiliZing alkali, alkaline earth, and transition metals ( Na+, Ca2+, Ba2+, Mg2+, Mn2+ and Co2+) as charge carriers in electrospray.Maltoheptaose, mannohexaose and laminarihexaose were taken as examples to investigate influence of metal ions on the extent of oligosaccharide fragmentation.The same types of fragmentation ions ( 0,2 A and 2,4 A) were obtained for barium- and calcium-adducted maltoheptaose.Mg2+ and Mn2+ had the similar influence ( 0,2 A, 2,4 A and 2,5 A ).Three cross-ring cleavage ions ( 1,4 A, 2,4 A and 2,5 A ) were generated in the spectrum of cobalt-associated maltoheptaose.But in the case of doping Na+into maltoheptaose, only 0,2 A ion was detected.It was found that the signals in the spectra of mannohexaose and laminarihexaose were worse than that in the spectrum of maltoheptaose, probably resulting from different numbers of adducted metal ions.The isomers, mannohexaose and laminarihexaose could be distinguished by ECD-MS in conjunction with the addition of Ca2+, Mg2+ or Co2+.The addition of Ca2+ was the best choice for analysis of oligosaccharides.