Keywords

1. Lignin valorisation
2. Two-dimensional chromatography
3. Depolymerized lignin analysis
4. Lignin structural characterization
5. Bio-based economy

With the global shift towards a circular and sustainable economy, the comprehensive characterization of lignin, an abundant natural polymer found in lignocellulosic biomass, is increasingly crucial. Scientists have recently made significant strides in this endeavor, as detailed in a groundbreaking study published in the distinguished journal “Analytica Chimica Acta” on February 1, 2024. The peer-reviewed article, led by Eliise Tammekivi and her colleagues from the Universite Claude Bernard Lyon 1, presents a potent off-line comprehensive two-dimensional (2D) chromatography approach, intertwining liquid chromatography (LC), supercritical fluid chromatography (SFC), and high-resolution mass spectrometry. This advanced methodological innovation promises to revolutionize the non-target analysis of depolymerized lignin, a critical step towards the valorisation of lignin into valuable chemicals and biomaterials.

The Research Breakthrough

Depolymerised lignin comprises an intricate mix of neutral monomers and oligomers, alongside numerous isomers, which historically have posed a challenge for separation and identification using conventional one-dimensional chromatographic techniques. In response, the team designed an off-line comprehensive 2D chromatographic method that combines the resolving power of LC and SFC, enhanced with high-resolution mass spectrometry. A 1-aminoanthracene column utilized in the second dimension facilitated discrete class separation, effectively categorizing lignin monomers, dimers, trimers, and tetramers. The separation was fine-tuned based on hydroxyl groups and steric hindrances, while the use of a pentafluorophenyl column in the first dimension greatly improved hydrophobic separation.

Crucially, this new approach overtakes the performance of traditional 1D SFC methods, particularly in the separation of elusive isomers. Isomer separation is critical, given that a staggering 77% of the detected compounds in the study presented at least one isomeric counterpart within the same lignin sample. This breakthrough not only provides a more comprehensive analysis but also a classification system for lignin sources that can facilitate comparison across different biomass origins and processing methodologies.

Integrating Advanced Data Analysis Methods

The study’s success was further enhanced by the integration of sophisticated data analysis tools such as MS-DIAL, SIRIUS, and Feature-Based Molecular Networking. These analytical techniques enabled researchers to rapidly visualize and scrutinize detected compounds, a capability that is particularly advantageous for characterizing separated isomers. As a result, the method yielded the first 2D LC plot that demonstrates a clear classification of lignin compounds, which is a substantial leap forward in lignin research.

The Implications for the Bio-Based Economy

Shifting away from petrochemicals towards bio-based alternatives is a critical component of achieving a circular economy. Lignin, which is often regarded as a byproduct of the fractionation process of lignocellulosic biomass, holds significant potential as a renewable source of aromatic compounds. The valorisation of lignin, which entails converting it into utilitarian chemicals or materials, hinges on an in-depth understanding of its structure. The new chromatographic approach laid out by Eliise Tammekivi et al. enhances the ability to deconstruct lignin’s intricate structure, thereby paving the way for the efficient development of valorisation processes.

Challenges and Opportunities

Despite the enthusiasm that surrounds this breakthrough, further research and optimization may be needed to transpose this method from an analytical setting to an industrial scale. The challenges of processing large volumes of biomass, the need for cost-effective and scalable methodologies, and adherence to sustainability guidelines are all pivotal factors that require attention as lignin valorisation transitions from a research initiative to practical applications.

The advancement also opens doors for collaborative efforts across disciplines, engaging chemists, material scientists, and industry professionals towards the collective goal of integrating lignin-derived products into the market. By highlighting the chemical composition and potential uses of different lignin sources, this methodology can aid in identifying the most promising candidates for various applications, such as adhesives, resins, or even biofuels.

Conclusion

The innovative 2D chromatography method developed by the research team at Universite Claude Bernard Lyon 1 marks a vital milestone in the non-target analysis of depolymerized lignin. As reflected by the DOI 10.1016/j.aca.2023.342157, this research, published in “Analytica Chimica Acta,” represents a transformative tool for the structural characterization of lignin. It is a development that could significantly impact the bio-based economy, providing a key to unlocking the intrinsic value of lignin and fostering the creation of sustainable products that contribute to environmental conservation and economic resilience.

References

Tammekivi, E. E., Batteau, M. M., Laurenti, D., Lilti, H., & Faure, K. (2024). A powerful two-dimensional chromatography method for the non-target analysis of depolymerised lignin. Analytica Chimica Acta, 1288, 342157. https://doi.org/10.1016/j.aca.2023.342157

Declaration of competing interests
The authors attest they have no known financial interests or personal relationships that might appear to influence the reported work.