An off-line pyrolysis/silylation procedure followed by GC-MS analysis was utilised for the detection of anhydrosugars evolved from cellulose and chitin in the form of trimethylsilyl (TMS) derivatives. In the case of cellulose, the performance of the following four silylating reagents was evaluated: hexamethyldisilazane (HMDS), trimethylsilyldiethylamine (TMSDEA) bis(trimethylsilyl)trifluoroacetamide (BSTFA) and trimethylsilylimidazole (TMSI). With all these silylating reagents, the main derivative of levoglucosan (LG) was the corresponding 2,3,4-tris-TMS ether. The 2- and 4-monoTMS ethers of LG, previously found as dominant species from on-line Py-GC-MS with HMDS, were not produced in the off-line procedure. The 2,4-bis-TMS ether of LG was still an important product in off-line pyrolysis/silylation with HMDS and TMSDEA, but a minor derivative with TMSI and BSTFA. Yields of LG evolved in the persilylated form were calculated and best reproducibility was observed for HMDS (12+-4 mg LG g~(-1) cellulose). Off-line pyrolysis/silylation of chitin with HMDS resulted in the predominant formation of 3,4-bis-TMS ether of 1,6-anhydro-2-acetamido-2-deoxyglucopyranose, while the 1,6-anhydro-4-O-(trimethylsilyl)-2-acetamido-2-deoxygluco-pyranose was tentatively identified as an important product in the on-line procedure.
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