A powerful two-dimensional chromatography method for the non-target analysis of depolymerised lignin

Area of Science:

• Analytical Chemistry
• Polymer Science
• Biomass Valorization

Background:

• Lignin, a byproduct of lignocellulosic biomass fractionation, is a key target for valorization in a circular economy.
• Accurate structural characterization of lignin is crucial for developing efficient valorization processes.
• Challenges in lignin analysis include complex mixtures of monomers, oligomers, and problematic isomers.

Purpose of the Study:

• To develop an advanced analytical method for the non-target analysis of depolymerized lignin.
• To improve the separation and identification of lignin compounds, particularly isomers.
• To enable comparative analysis of different lignin sources and processing methods.

Main Methods:

• An off-line comprehensive two-dimensional (2D) chromatography method combining liquid chromatography (LC) and supercritical fluid chromatography (SFC).
• Utilized a 1-aminoanthracene column in the second dimension for class separation (monomers to tetramers) and separation by hydroxyl groups/steric effects.
• Employed a pentafluorophenyl column in the first dimension for improved separation based on hydrophobicity.
• Integrated advanced data analysis tools (MS-DIAL, SIRIUS, Feature-Based Molecular Network) for compound visualization and isomer characterization.

Main Results:

• Achieved superior separation of lignin compounds, including isomers, compared to 1D SFC.
• Demonstrated class separation of lignin monomers, dimers, trimers, and tetramers.
• Successfully visualized and studied detected compounds and their isomers using integrated data analysis.
• Identified that 77% of detected compounds had at least one isomer within the same lignin sample.

Conclusions:

• Developed the first 2D LC plot for classifying lignin compounds, enabling comparison of lignin sources and processing.
• The method significantly improves the separation of complex lignin mixtures and isomers.
• This technique is vital for advancing lignin valorization and the circular economy.