Guard pa 20 column

The monosaccharide composition of NHSP was analyzed by high-performance anion exchange chromatography (HPAEC) coupled with a pulsed amperometric detector (PAD). Neutral sugars and uronic acids were released by hydrolysis with 10% H₂SO₄ for 2.5 h at 105°C. The NHSP was then diluted 50-fold, filtered, and injected into an HPAEC system (Dionex ISC 3000; United States) with an amperometric detector, AS50 autosampler, CarbopacTMPA-20 column (4 × 250 mm; Dionex), and guard PA-20 column (3 × 30 mm). Neutral sugars and uronic acids were separated in isocratic 5 mM NaOH (carbonate free and purged with nitrogen) for 20 min and then subjected to a NaAc gradient (0–75 mM) in 5 mM NaOH for 15 min. The columns were washed with 200 mM NaOH for 10 min to remove carbonate and eluted for 5 min with 5 mM NaOH for re-equilibration before the next injection. The total analysis time was 50 min and the flow rate was 0.4 ml/min (Bian et al., 2012 (link)). Calibration was performed using standard solutions of L-arabinose, D-xylose, D-glucose, D-mannose, D-galactose, glucuronic acid, and galacturonic acid.

The chemical component analysis of untreated and treated samples was performed according to NREL procedures LAP-002 [59 ]. The monomer sugars were analyzed by high-performance anion exchange chromatography (HPAEC) system (Dionex ICS 3000, USA) with pulsed amperometric detector, AS50 autosampler, the Carbopac™ PA-20 column (4 × 250 mm, Dionex) and the guard PA-20 column (3 × 30 mm, Dionex). Neutral sugars and uronic acids were separated in a 5 mM NaOH (isocratic; carbonate free and purged with nitrogen) for 20 min, followed by a 0–75 mM NaAc gradient in 5 mM NaOH for 15 min. Then the columns were washed with 2 mM NaOH to remove carbonate for 10 min, followed by a 5 min of elution with 5 mM NaOH to re-equilibrate the column before the next injection. The total analysis time was 50 min and the flow rate was 0.4 ml/min. The content of HCA was determined using the procedure outlined in Ref. [14 (link)].

The chemical compositions of the untreated corn stover, the acid-steam-exploded corn stover and the alkaline ethanol post-treated samples, AL as well as EHR were determined according to the National Renewable Energy Laboratory (NREL) protocol [52 ]. The total lignin content was the summation of acid-soluble lignin and acid-insoluble lignin. The sugars were quantified on a HPAEC system (Dionex ICS3000, US) equipped with a pulsed amperometric detector, an AS50 autosampler, a Carbopac TM PA-20 column (4 × 250 mm, Dionex), and a guard PA-20 column (3 × 30 mm, Dionex) according to a previously published method [41 (link)]. The sugar fractions were separated in a 5 mM NaOH isocratic (carbonate free and purged with nitrogen) condition for 20 min, followed by a 0–75 mM NaAc gradient in 5 mM NaOH for 15 min. Then the columns were washed with 200 mM NaOH to remove carbonate for 10 min, and followed a 5 min elution with 5 mM NaOH to re-equilibrate the column before the next injection. The total analysis time was 50 min and the flow rate was 0.4 mL min⁻¹. The analysis of sugar composition in the present study was run in duplicate.