Evidence for oligomers in pyrolysates of microcrystalline cellulose

Microcrystalline cellulose was analysed by platinum filament pyrolysis desorption chemical ionisation mass spectrometry (DCI-MS) under ammonia chemical ionisation conditions. This polysaccharide was also pyrolysed on a preparative scale as well as by off-line Curie-point pyrolysis and subsequently analysed by ammonia DCI-MS. The DCI-MS data of the native polysaccharide show ion series corresponding to ammonium adduct ions of anhydrocello-oligosaccharides up to anhydrocello-hexaose. In the preparative-scale and the off-line Curie-point pyrolysates up to the pentamer could be detected. Related ion series corresponding to the ammonia adducts of ring fragments left on the saccharide chain were also seen. It is uncertain whether these compounds are formed during pyrolysis directly from the native polymer or arise from the corresponding anhydro-oligosaccharides during the ionisation process. The three pyrolysis methods tested yield comparable results with respect to the pyrolysis products formed, which indicates that the mechanism of formation of anhydrocello-oligosaccharides from cellulose is a generally significant process. Curie-point pyrolysis-gas chromatography data should be interpreted with caution since the oligomeric part of the pyrolysate is not monitored by this method.