Determination of Carbohydrates in Acid Hydrolysates of Wood

Importance of the Topic

The development of sustainable biofuel production requires accurate monitoring of carbohydrate breakdown in wood biomass. High-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) enables rapid, sensitive quantification of monosaccharides and oligosaccharides released during acid hydrolysis. Improved resolution of challenging sugar pairs such as rhamnose and galactose supports process optimization and quality control in biorefineries.

Objectives and Study Overview

This application note presents two rapid HPAE-PAD methods for determining individual carbohydrates in acid hydrolysates of wood. The study focuses on a new Thermo Scientific Dionex CarboPac SA10-4µm column with reduced resin particle size and hardware modifications to achieve high-efficiency separation, especially of the rhamnose-galactose pair, and to simplify handling of high-concentration samples.

Methodology and Instrumentation

A Thermo Scientific Dionex ICS-5000+ HPIC system equipped with a Dionex CarboPac SA10-4µm analytical column (4×250 mm), guard column, and a 62 mil PTFE gasket in the electrochemical cell was used. A 1 mM KOH eluent was generated on-line by the Dionex EGC III KOH cartridge with CR-ATC trap column. A 0.4 µL internal injection loop and reduced electrode sensitivity enabled 2- to 50-fold sample dilutions. Two methods were defined:

• Method 1: 1.5 mL/min, 45 °C, run time <8 min for eight common sugars
• Method 2: 1.2 mL/min, 30 °C, run time 14 min to resolve galactose and rhamnose plus up to eleven sugars

Main Results and Discussion

Method 1 achieved baseline separation of fucose, sucrose, arabinose, galactose, glucose, xylose, mannose and fructose with >40 % higher peak efficiency and signal-to-noise than the standard 6 µm column. Method 2 successfully resolved the galactose-rhamnose pair and quantified eleven carbohydrates with retention time RSD <0.3 % and peak area RSD <3.5 %. Linearity was demonstrated from 0.05 to 2.4 g/L (r2 >0.998), and recoveries in spiked wood liquor/rinsate ranged from 71 to 103 %. Column-to-column reproducibility for efficiency, resolution, and retention time showed RSD <5 %.

Practical Benefits and Applications

These methods deliver rapid, reproducible carbohydrate profiling in complex wood hydrolysates with reduced sample preparation and dilution steps. High-pressure capability of the ICS-5000+ supports the 4 µm column’s backpressure. The approaches facilitate routine monitoring of fermentable sugar yield in biomass-to-biofuel conversion and can be integrated into quality assurance/quality control workflows.

Future Trends and Potential Uses

Further trends include integration of high-throughput autosampler workflows, coupling HPAE-PAD with mass spectrometry for enhanced structural information, microfluidic column formats for lower solvent consumption, and application of machine learning for automated peak identification and concentration prediction.

Conclusion

The described HPAE-PAD methods using the Dionex CarboPac SA10-4µm column and on-line KOH generation provide fast, accurate, and high-resolution analysis of wood hydrolysate carbohydrates. Two complementary methods address both routine sugar profiling and detailed resolution of critical sugar pairs, supporting efficient biofuel production.

Reference

1. Larsen E. Biofuel Production Technologies: Status, Prospects and Implications for Trade and Development. UNCTAD, 2008.
2. Demirbas A. Biofuels: Securing the Planet’s Future Energy Needs. Springer, 2009.
3. Stephen JD, Mabee WE, Saddler JN. Will Second-Generation Ethanol Compete with First-Generation Ethanol? Biofuels, Bioproducts and Biorefining 2012, 6(2), 159–176.
4. Sluiter JB et al. Compositional Analysis of Lignocellulosic Feedstocks. J Agric Food Chem 2010, 58(16), 9043–9053.
5. Davis MW. A Rapid Modified Method for Compositional Carbohydrate Analysis of Lignocellulosics by HPAEC/PAD. J Wood Chem Technol 1998, 18(2), 235–252.
6. Thermo Scientific Application Note 282: Rapid and Sensitive Determination of Biofuel Sugars by Ion Chromatography. Thermo Fisher Scientific, 2012.
7. Thermo Scientific Application Update 192: Carbohydrate Determination of Biofuel Samples. Thermo Fisher Scientific, 2014.
8. Thermo Scientific Technical Note 71: Eluent Preparation for HPAE-PAD. Thermo Fisher Scientific, 2013.