Characterization of Soluble and Insoluble Lignin Oligomers by Means of Ultrahigh Resolving Mass Spectrometry

Abstract

Lignin is a complex macromolecule that possesses a high potential for various material-based applications in the near future. In order to retrieve this potential, more detailed knowledge about the structural composition of lignin is required. One possible way to solve this problem is the application of ultrahigh resolving analysis methods such as Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). In most studies from the last years, mainly dissolved lignin compounds, which only represent a fraction of the overall sample, were utilized for MS investigations. In this study, both soluble and insoluble lignin compounds of three different lignins (Kraft and Lignoboost lignins) were analyzed by electrospray ionization (ESI) and graphite-assisted laser desorption/ionization (GALDI) in combination with FT-ICR-MS. The different MS analyses demonstrated that ESI- and liquid GALDI-MS analyses can assist in the characterization of lignin molecules, which possess a high solubility in solvents of high polarity. In contrast, solid GALDI-MS provides insights about less polar molecules that have a low solubility in most solvents. Due to this higher molecular range of analyzable lignin compounds, the novel results will, hopefully, help to improve our understanding of the lignin structure and to utilize this interesting biopolymer in a more expedient and efficient way in the future.

Chemometric Combination of Ultrahigh Resolving Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy for a Structural Characterization of Lignin Compounds

“…as they are still soluble, despite their considerable molecular size. A similar trend was also observed for different Kraft and LignoBoost lignin samples, as demonstrated in a previous work from our research group. Hence, the results of the LBL fractions, once again, show the necessity to combine ESI- and GALDI-MS analyses to obtain realistic and comprehensive insights into complex biomass samples.…”

“…Data calibration and evaluation of the FT-ICR-MS and tandem MS experiments were conducted according to previously published procedures. , …”

“…In contrast, HR-MS gives the opportunity to study the complexity of lignin compounds, with regard to the molecular weight, oligomer size, linkage types, and the presence of functionalities in lignin molecules from different sources. − Various research groups were able to demonstrate that HR-MS in combination with electrospray ionization (ESI) ,− atmospheric pressure chemical ionization (APCI) and photo ionization (APPI) or matrix-assisted laser desorption/ionization (MALDI) − can be utilized to study, for instance, Kraft lignins, organosolv lignins, or electro- and photochemically degraded lignins. In addition, tandem MS analyses are helpful to obtain detailed structural information about different lignin molecules. ,,,,− Comprehensive investigations of lignins and other complex mixtures are possible by utilizing the most powerful MS technique, Fourier transform ion cyclotron resonance MS (FT-ICR-MS). , For example, the potential of FT-ICR-MS for lignin analyses was recently demonstrated by characterizing soluble and insoluble compounds from different Kraft and LignoBoost lignins (LBL) with the help of ESI and graphite-assisted laser desorption/ionization (GALDI). − …”

“…27,29,34,35,43−47 Comprehensive investigations of lignins and other complex mixtures are possible by utilizing the most powerful MS technique, Fourier transform ion cyclotron resonance MS (FT-ICR-MS). 48,49 For example, the potential of FT-ICR-MS for lignin analyses was recently demonstrated by characterizing soluble and insoluble compounds from different Kraft and LignoBoost lignins (LBL) 50 with the help of ESI and graphite-assisted laser desorption/ionization (GALDI). 51−54 Despite the advancements in the field of lignin characterization by NMR and HR-MS in the last years, to date, a holistic characterization of lignin and its complex structure seems only possible if results from different analytical techniques are combined.…”

Highly Selective Alkaline Oxide Promoted Ni/silica for the Production of Cyclohexanol/‐one from Lignin‐Derived Guaiacol

“…For decades now, catalytic hydrodeoxygenation (HDO) has been one of the most promising fields in research to upgrade bio‐oils from wood pyrolysis to green fuels and basic chemicals. However, the enormous potential of sustainable bio‐based carbon sources is currently still used for thermal purposes, such as 80 million tons/year of lignin from the paper industry, which could be exploited as raw material in the chemical industry [2,3] …”