Mass spectrometric studies of cellulose ethers
Abstract: Cellulose based derivatives, such as cellulose ethers, today find many applications in a diverse range of fields. The numerous applications put high demands on the technological performance of the cellulose ethers. In order to be able to control the technological properties it is necessary to develop analytical methods by, which they can be correlated to the chemical structure. In some cases variations in the technological properties cannot be explained by the chemical characterisation methods available today. Thus, it is of high importance to investigate the suitability of new analytical techniques for chemical characterisation of cellulose ethers. In this thesis matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) and nanoelectrospray ionisation (nano-ESI)-MS were studied as analytical techniques for cellulose ethers. Among the results, MALDI tandem mass spectrometry (MS/MS) and nano-ESI-MS/MS were demonstrated as exceptionally useful tools for the structure analysis of cellulose ether oligosaccharides. Nano-ESI-MS/MS was employed to characterise the selectivity of a cellulose depolymerising enzyme, endoglucanase, on methyl cellulose (MC). Novel dialkylamine derivatives of cellulose ether oligosaccharides were shown to increase the sensitivity in both MALDI- and nano-ESI-MS, and to facilitate structure analysis by MS/MS. Studies of the molar mass distribution of partially depolymerised MC were performed by size-exclusion chromatography semi-online to MALDI-MS. The sample preparation method for MALDI was found to have a significant influence on the outcome of the analysis. Furthermore, a simple experiment showed that, the combination of MALDI-MS and partial acidic depolymerisation could be used to distinguish between cellulose ethers of different degrees of substitution.
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