Hemicellulose monosaccharide analysis by GC-MS and lignin monomer detection by HPLC

GC/MS analysis was conducted with SHIMADZU GCMSQP2010 Plus according to Xu et al. (2012). This analysis used a Restek Rxi-5 ms, 30 m × 0.25 mm ID × 0.25 um df column. Monosaccharide standards including L-rhamnose, L-arabinose, L-fucose, D-xylose, D-galactose, D-glucose, and D-mannose, were obtained from Sinopham Chemical Reagent Co., Ltd. The GC-MS Analytical Conditions are listed as the follows: Carrier gas: He. Injection Method: Split. Injection port: 250°C, Interface: 250°C. Injection Volume: 1.0 μL. The temperature program: from 170°C (held for12 min) to 220°C (held for 8 min) at 3°C/min. Ion source temperature: 200°C, ACQ Mode: SIM. The mass spectrometer was operated in the EI mode with ionization energy of 70 ev. Mass spectra were acquired with full scans based on the temperature program from 50 to 500 m/z in 0.45 s. Calibration curves of all analytes routinely yielded correlation coefficients 0.999 or better. Peaks were identified by mass profiles and/or retention times of standards. Monosaccharides were quantified based on standard curves.

Lignin monomers were determined by HPLC as previously described by Xu et al. (2012). Standard chemicals, including p-Hydroxybenzaldehyde (H), guaiacy (G), and syringaldehyde (S), were purchased from Sinopharm Chemical Reagent Co., Ltd. The samples after pretreatment were used to detect lignin monomers by HPLC. The solution was filtered with membrane filter (0.22 μm). The filtered solution was injected into HPLC with 20 μL (Waters 1525 HPLC) column Kromat Universil C18 (4.6 mm × 250 mm, 5 μm) operating at 28°C with CH₃OH: H₂O: HAc (25:74:1, v/v/v) carrier liquid (flow rate: 1.1 mL/min).