Deuterium effect on ionization and fragmentation patterns of monosaccharides ionized by atmospheric pressure chemical ionization

Glucose, galactose, and mannose in H₂O and D₂O were ionized by an atmospheric pressure chemical ionization (APCI) method. Isotope effects on fragmentation patterns of the monosaccharides were examined by deuterium replacement of the -OH groups to distinguish the isomers with a single mass spectrometer. The most abundant ions were the M+H₂O]⁺ and M_D5+D+D₂O]⁺ for using H₂O and D₂O as solvent and eluent, respectively. Major fragment ions were the M−OH]⁺ and M−OH−H₂O]⁺ in H₂O, while those in D₂O were the M_D5+D−D₂O]⁺ and M_D5+D−2D₂O]⁺. The differences in the product ions generated in H₂O and D₂O were due to enhancement of the strength of hydrogen bonding by the deuterium replacement. Variations of the ion intensity ratios of the M−OH]⁺/M−OH−H₂O]⁺ and M_D5−OD]⁺/M_D5−OD−D₂O]⁺ with the fragmentor voltage showed different trends depending on the kind of monosaccharides. By comparing the ion intensity ratios of the M+H₂O]⁺/M⁺, M_D5+D+D₂O]⁺/M_D5+D]⁺, M−OH]⁺/M−OH−H₂O]⁺, and M_D5+D−D₂O]⁺/M_D5+D−2D₂O]⁺, it was possible to distinguish the isomers of monosaccharides.