Characterisation of polysaccharides by in-source pyrolysis positive- and negative-ion direct chemical ionisation-mass spectrometry.

Series of oligosaccharide ions have been generated from a range of polysaccharides by the application of in-source pyrolysis mass spectrometry, using both ammonia positive-ion chemical ionisation and negative-ion chlorine-nucleophilic-addition ionisation. Glucans with alpha-(1----6), beta-(1----6), alpha-(1----4), beta-(1----4), beta-(1----3), and beta-(1----2) linkages were studied, together with pentosans, xyloglucans, and an arabinogalactan. The series of ions correspond to intact, desorbed oligosaccharides with a terminal anhydro-sugar unit, and to similar oligosaccharides with attached sugar ring-cleavage fragments. The ions generated are dependent on the position of the linkage and ring size, and retain significant information on the structure of the original polysaccharide.