The introduction of size-exclusion chromatography (SEC) analysis of polysaccharides prior to MALDI mass
spectroscopy accounts for the determination of the molecular mass of the repeating unit when neutral homopolymers
are investigated. In the case of natural polysaccharides characterised by more complicated structural features
(presence of non-carbohydrate substituents, charged groups, etc.), this mass value usually is in agreement with more
than one sugar composition. Therefore, it is not sufficient to give the correct monosaccharidic composition of the
polysaccharide investigated. To solve this problem, MALDI spectra were recorded on the permethylated sample and
post-source decay experiments were performed on precursor ions. In this way, the composition (in terms of Hex,
HexNAc, etc.), size and sequence of the repeating unit were determined.
