POSITIVE-ION AND NEGATIVE-ION MATRIX-ASSISTED-LASER-DESORPTION IONIZATION MASS-SPECTROMETRY OF SACCHARIDES/

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) of oligosaccharides and polysaccharides has been investigated in detail, It is demonstrated that cationized species of oligosaccharides , [M+Na](+) and [M+K](+), are dominant products under the MALDI condit ion, and negative ions of oligosaccharides are not formed to any signi ficant extent in this process, The molecular masses of polysaccharides are similarly determined by positive- and negative-ion MALDI-MS with the help of column chromatography. The distinction between positive- a nd negative-ion MALDI mass spectra of oligo-and polysaccharides indica tes that the MALDI processes for saccharides vary with molecular mass. The matrix plays a more important role in the ionization process for oligosaccharides, while in the desorption process for polysaccharides. (C) 1998 John Wiley & Sons, Ltd.