Fig 2.1 and Fig 2.2

Chromatogram of initial sugars and some degradation products measured using HPLC-RID and HPLC-UV.

From Fig 2.1 shows the retention time (Rt): 9.050, 9.693 and 10.555 corresponding to Glucose, Xylose and Arabinose. 

From Fig 2.2 shows some degradation products: 11.145 min, 13.574 min, 14.651 min , 18.675 min and 19.983 min corresponding to acetic acids, formic acid, lactic acids, butiric acids and propionic acids.


The monosaccharides were quantified in the liquid fractions (the liquid fractions obtained after the applied hydrolysis experiments and the liquid fractions from the acid digestion of the exhausted solids) using an Aminex® HPX-87H ion exclusion column (Bio-Rad) installed in a Shimadzu LC-2050C separation module. A refractive index detector (RID) was used to quantify the monosaccharide concentration using a mobile phase of 25 mM sulphuric acid solution (HPLC quality) at a flow rate of 0.6 mL/min. The column and the RID were maintained at 50°C. A multistandard calibration solution was prepared by diluting single standards (glucose, xylose, arabinose and cellobiose) commercially available with a purity > 95% (Sigma, Aldrich, Spain).The most standardized by-products generated during the hydrolysis of the residual biomass  were analyzed in the form of volatile organic acids (VFA), including acetic acid, formic acid, levulinic acid, lactate, propionate, butyrate, iso-butyrate, valerate, iso-valerate, iso-caproate and hexanoate. HPLC with a UV detector (model UV-2600i, Shimadzu, Japan) at 210 nm was used for analysis. Sodium L-lactate (Sigma-Aldrich) and a mixture of VFA (Sigma-Aldrich) were used as reference standards.