Contributions to Lignomics: Stochastic Generation of Oligomeric Lignin Structures for Interpretation of MALDI–FT‐ICR‐MS Results

Abstract

The lack of standards to identify oligomeric molecules is a challenge for the analysis of complex organic mixtures. High‐resolution mass spectrometry—specifically, Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR MS)—offers new opportunities for analysis of oligomers with the assignment of formulae (CxHyOz) to detected peaks. However, matching a specific structure to a given formula remains a challenge due to the inability of FT‐ICR MS to distinguish between isomers. Additional separation techniques and other analyses (e.g., NMR spectroscopy) coupled with comparison of results to those from pure compounds is one route for assignment of MS peaks. Unfortunately, this strategy may be impractical for complete analysis of complex, heterogeneous samples. In this study we use computational stochastic generation of lignin oligomers to generate a molecular library for supporting the assignment of potential candidate structures to compounds detected during FT‐ICR MS analysis. This approach may also be feasible for other macromolecules beyond lignin.

Lignin Depolymerization: A Comparison of Methods to Analyze Monomers and Oligomers

“…[112,113] Consequently, common MALDI approaches fail to cover the real mass distribution on the whole broad mass range of lignin and of heavy liquefaction products. [56,57] MALDI or LDI remains an interesting method for oligomer analysis if LDI is combined with high resolution (HR) MS and if careful ionization conditions are used. [114] (MA)LDI-HRMS can provide the elemental formula of oligomers and even their chemical structure if it is combined with an advanced stochastic modeling approach.…”

“…[55] Indeed, m/z higher than 2000 are poorly resolved in previous work on MALDI-TOF analysis of lignin. MALDI is rather used for lignomic analysis of oligomers [57,58] with higher resolution mass spectrometers (resolution in the range of 200 000) than for TOF MS.…”

“…[50] Laser desorption ionization mass spectrometry (LDI-MS) as well as other ionization techniques has been used on lignin and its products [51][52][53][54][55] for "lignomic" studies. [56,57] Computational and graphical methods are currently used to elucidate the composition of oligomers. [57,58] LDI has been combined with high resolution mass spectrometry (HRMS) to analyze lignin and wood bio-oil, [59,60] biochar [61] and on lignin pyrolysis intermediates.…”

“…[56,57] Computational and graphical methods are currently used to elucidate the composition of oligomers. [57,58] LDI has been combined with high resolution mass spectrometry (HRMS) to analyze lignin and wood bio-oil, [59,60] biochar [61] and on lignin pyrolysis intermediates. [47] Matrix assisted LDI (MALDI) combined with time of flight mass spectrometry (TOF MS) has been used on lignin liquefaction products.…”

“…A tentative description of oligomeric structure is derived from MALDI-TOF MS analysis, but other HRMS techniques (like Fourier transform ion cyclotron reso-nance MS, FTICR-MS) are more recommended, in comparison to TOF MS, for elucidating the chemical composition of lignin oligomers. [57,58] UV/Vis spectroscopy has been used to quantify soluble lignin. [64,65] Chen et al have monitored lignin electrochemical depolymerization using UV spectroscopy.…”