EFFECT OF PRETREATMENT ON PYROLYSIS FIELD-IONIZATION MASS-SPECTROMETRIC DATA OF (4-O-METHYL-D-GLUCURONO)-D-XYLAN FROM BEECH WOOD

The thermal degradation of (4-O-methyl-D-glucurono)-D-xylan in the Na+ and H+ form as well as the water-soluble fraction of this material before and after hydrolysis was studied by pyrolysis-field ionization mass spectrometry (Py-FIMS). Results indicated the presence of 2-furaldehyde, 2-furoic acid, 1,4:2,3-dianhydro-D-pentose and/or other C5H6O3 compounds, 5-hydroxymethyl-2-furaldehyde, 1,4-anhydro-D-pentose, 2,3-butandione, and ions m/z 164 (C6H12O5) and 192 (C7H12O7), the exact chemical nature of which are unknown. Structure C6H12O5 was formed from the Na+ form to a greater degree than from the H+ form. The acidic form of xylan showed two maxima of 2-furoic acid formation at 300 and 335-degrees-C in comparison to one at 330-degrees-C for material in the Na+ form and the soluble fraction. The Py-FI mass spectrum of hydrolyzed material did not indicate the presence of a number of compounds observed with non-hydrolyzed material but showed instead peaks at m/z 73 and 144 which originate from anhydrosugars and compounds typical of the Py-FIMS analysis of monosaccharides. The maximal ion current for hydrolyzed material was at 130-degrees-C while for the unhydrolyzed materials the maximum was in the range of 290-330-degrees-C.