NMR and ESI–MS spectrometry characterization of autohydrolysis xylo-oligosaccharides separated by gel permeation chromatography

Chemical structure determination of xylo-oligosaccharides obtained by common production pathway is difficult, since the products mixture must be separated and purified into individual chemicals. In the present study, gel permeation chromatography was used to efficiently separate and purify the xylo-oligosaccharides produced by biomass autohydrolysis for the chemical structural evaluation. Results showed that the separation obtained high purity (85.2–94.5%) xylo-oligosaccharides with individual component. The separated samples were further characterized by ESI–MS and NMR, which revealed that the samples were non-substituted xylobiose and acetylated xylo-oligosaccharides with degree of polymerization from 3 to 6. The combined 1H, 13C and two-dimensional proton-detected heteronuclear single quantum (2D HSQC) NMR spectra results suggested that acetyl groups only attached to the internal units of xylo-oligosaccharides after autohydrolysis, and no acetylated non-reducing ends were detected.