Comparison of the Sensitivities of Various Derivatives of Oligosaccharides in LC/MS with Fast Atom Bombardment and Electrospray Ionization Interfaces

Sensitivities of the following derivatives of oligosaccharides in MS and LC/MS with frit FAB and ESI interfaces were compared under the conditions where samples were supplied to the probes in solutions at constant rates: 2-aminopyridine, 4-aminobenzoic acid ethyl ester (ABEE), 1-phenyl-3-methyl-5-pyrazolone (PMP) as well as 4-methoxyphenyl analogue, 2-aminoethanethiol, and 2-aminobenzenethiol. In FAB-MS, maltopentaose labeled with ABEE gave the most abundant [M + H]+ ions in positive ion mode when ionized in thioglycerol or glycerol matrix supplied in 50% (v/v) aqueous methanol. The lowest limit of detection was obtained for this compound in these matrices in water. The [M - H]- ion in negative ion mode was also abundant in all matrices examined in both 50% (v/v) aqueous methanol and water. On the other hand PMP derivatives gave the highest sensitivities in ESI-MS under the optimized conditions. On the basis of these findings, authentic oligosaccharides and oligosaccharides derived from a few glycoprotein samples were analyzed by LC/MS with frit FAB and ESI interfaces. The results indicated the usefulness of these derivatives for simultaneous microanalysis of oligosaccharides.