Liquid Secondary Ion Mass Spectrometry of Methyl Glycosides of Oligosaccharides Using Matrices Containing Carboxamides

• Published in: Rapid communications in mass spectrometry Vol. 10; no. 13; pp. 1661 - 1667
• Main Authors: Kováčik, Vladimír, Hirsch, Jan, Zorić, Sandra, Grützmacher, Hans-Friedrich
• Format: Journal Article
• Language: English
• Published: London Heyden & Son Limited 1996
• Subjects: Carbohydrate Sequence; Glycosides - analysis; Kinetics; Molecular Sequence Data; Molecular Weight; Oligosaccharides - analysis; Spectrometry, Mass, Secondary Ion
• ISSN: 0951-4198; 1097-0231
• DOI: 10.1002/(SICI)1097-0231(199610)10:13<1661::AID-RCM680>3.0.CO;2-6

Intense cluster ions corresponding to proton‐bound hetero‐dimers of an amide molecule and an oligosaccharide molecule are observed in the liquid secondary ion mass spectra of methyl glycosides of oligoxylans if a solution of an aliphatic carboxamide in glycerol is used as the liquid matrix. These cluster ions are particularly abundant and persist for a long period if urea (U) or thiourea (TU) is used as the matrix additive. In these cases, cluster ions containing more than one molecule of U or TU and two oligosaccharide molecules are also observed. The intense signal due to the proton‐bound hetero‐dimer between U or TU and the oligosaccharide can be used with advantage for a molecular weight determination. The bonding interactions between a protonated saccharide molecule and a molecule U or TU in the proton‐bound hetero‐dimers are so strong that the urea molecules remain attached to the fragment ions during the decay of metastable cluster ions and even during collision‐induced dissociation. Thus, the mass‐analysed ion kinetic energy spectra of these proton‐bound hetero‐dimers are dominated by abundant cluster ions [Bn+U] and [Ym+U] arising from cleavage of the glycosidic bonds within the oligosaccharides. The collisionally‐activated mass spectra of the proton‐bound hetero‐dimers additionally contain peaks of the free ions Bn and Ym. Therefore, these spectra clearly reflect the arrangement of the monosaccharide residues in the oligosaccharide and can be used conveniently for structural analysis.