Carbopac sa 10 column

The general composition of the bark residues, which comprised wood particles, ash, extractives, lignin, cellulose, and hemicellulose content, was determined using the National Renewable Energy Laboratory (NREL) protocols: TP‐510‐42618, TP‐510‐42619, TP‐510‐42620, and TP‐510‐42622 (Hames et al., 2008; Sluiter, Hames, et al., 2005; Sluiter et al., 2008b; Sluiter, Ruiz, Scarlata, Sluiter, & Templeton, 2005). Briefly, the method for determining the ash composition was based on the percentage of residue remaining after dry oxidation at 550–600°C. All results are reported relative to the 105°C oven dry weight of the sample. The extractive composition was carried out using a Soxhlet apparatus with ethanol at reflux for 16–24 hr. The lignin content was measured by UV‐Vis spectroscopy (Hach DR6000) after a two‐step acid hydrolysis to fractionate the biomass into forms that are more easily quantified. The monomeric sugars constituting cellulose and hemicellulose were quantified by ion chromatography (Dionex ICS‐5000) with the Dionex CarboPac SA‐10 column and the electrochemical detector.

Each cell wall extract and intact cell wall sample was hydrolysed with 2M trifluoroacetic acid (TFA) for 1h at 100 °C. The acid was evaporated under vacuum and the monosaccharides were resuspended in 2ml of ultra-purified water. Monosaccharide profiles were analysed by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) on a CarboPac SA10 column (DX-500 system, Dionex^®) using a mixture of 99.2% water and 0.8% (v/v) 150mM NaOH as eluent (1ml min^–1). The monosaccharides were detected with a post-column addition of base with 500mM NaOH (1ml min^–1).

The concentrations of polysugars and monosugars in the hydrolysis liquor and soda liquor were determined using ion chromatography, Dionex, ICS 5000, Thermofisher Scientific, equipped with CarboPac™ SA10 column and an electrochemical detector (ED) (Dionex-300, Dionex Corporation, Canada). Deionized water and KOH Eluent Generator (EGC 500 KOH, ThermoScientific) were used to generate an eluent of 1.00 mM of KOH at a flow rate of 1.2 mL/min. The column temperature was set at 30 °C. The monosugar concentration in the liquors was measured without pretreating the liquors but after adjusting pH of the liquors to 7. The hydrolysis and soda liquors were acid-hydrolyzed under the conditions of 4% sulfuric acid at 121 °C for 1 h in an oil bath (Hakke S45, Instruments, Inc., Portsmouth, N.H., USA) based on the method described in the literature [12 (link)]. This acid hydrolysis is widely used for converting oligosugars to monosugars [4 (link), 12 (link)]. Afterward, the concentration of monosugars in the hydrolysis liquors was measured as stated above, and it reflected the concentration of total monosugars (after conversion of oligosugars to monosugars) in the hydrolysis and soda liquors. The concentrations of polysugars were determined via subtracting total sugar concentrations from monosugar concentrations.