Energy‐Resolved Mass Spectrometry as a Tool for Identification of Lignin Depolymerization Products

Abstract

Lignin is the largest source of bio-based aromatic compounds in nature, and its valorization is essential to the sustainability of lignocellulosic biorefining. Characterizing lignin-derived compounds remains challenging due to the heterogeneity of this biopolymer. Tandem mass spectrometry is a promising tool for lignin structural analytics, as fragmentation patterns of model compounds can be extrapolated to identify characteristic moieties in complex samples. This work extended previous resonance excitation-type collision-induced dissociation (CID) methods that identified lignin oligomers containing β-O-4, β-5, and β-β bonds, to also identify characteristics of 5-5, β-1, and 4-O-5 dimers, enabled by quadrupole time-of-flight (QTOF) CID with energy-resolved mass spectrometry (ERMS). Overall, QTOF-ERMS offers in-depth structural information and could ultimately contribute to tools for high-throughput lignin dimer identification.

Quantification of Phenolic Hydroxyl Groups in Lignin via 19F NMR Spectroscopy

“…29 The 5-5 GG model compound was produced according to previously published methods. 30 Model Compound and Lignin Derivatization. The substrate (either lignin or a model compound, typically between 20 and 40 mg) was loaded into a 10 mL vial with a stir bar.…”

“…4-Propylsyringol was synthesized from 4-allyl-2,6-dimethoxyphenol (Sigma-Aldrich) . The 5-5 GG model compound was produced according to previously published methods …”

Next Challenges for the Comprehensive Molecular Characterization of Complex Organic Mixtures in the Field of Sustainable Energy

“…Among the biopolymers mentioned previously, lignin is the second largest component of lignocellulosic biomass, accounting for 15% to 30% of the mass, and it is generally considered to be composed of three phenylpropane units [139][140][141][142]. However, tandem mass spectrometry is a promising tool for lignin structural analysis, as fragmentation patterns of model compounds can be extrapolated to identify characteristic moieties in complex samples [143]. Zhang et al applied tandem mass spectrometry on alkali lignin pyrolysis oil after the sequential extraction method.…”

“…Moreover, the current lignin depolymerization technique also made it possible to produce partially deoxygenated dimeric and oligomeric fractions for use in liquid fuel applications and other renewable energy sources [145]. Recently, Dong et al used beam-type CID with energy-resolved mass spectrometry (ERMS) to apply previous resonance excitation type CID techniques that identified lignin oligomers containing β-O-4, β-5, and β-β bonds to additionally identify features of 5-5, β-1, and 4-O-5 dimers [143]. Overall, the beam-type ERMS provides comprehensive structural data and may eventually help develop instruments for high-throughput lignin dimer detection [143].…”

“…Recently, Dong et al used beam-type CID with energy-resolved mass spectrometry (ERMS) to apply previous resonance excitation type CID techniques that identified lignin oligomers containing β-O-4, β-5, and β-β bonds to additionally identify features of 5-5, β-1, and 4-O-5 dimers [143]. Overall, the beam-type ERMS provides comprehensive structural data and may eventually help develop instruments for high-throughput lignin dimer detection [143].…”