Elucidation of the complex molecular structure of wheat straw lignin polymer by atmospheric pressure photoionization quadrupole time‐of‐flight tandem mass spectrometry

Abstract

Wheat straw lignin was extracted using the novel CIMV procedure which selectively separates the cellulose, hemicelluloses and lignin. Solid-state (13)C NMR experiments using cross polarization/magic angle spinning (CP/MAS) were carried out on the extracted wheat straw lignin and some structural indices were revealed. Atmospheric pressure photoionization mass spectrometry (APPI-MS) has proven to be a powerful analytical tool capable of ionizing small to large lignin oligomers, which cannot be ionized efficiently by atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). The APPI mass spectra of the extracted wheat straw lignin were recorded in the positive and negative ion modes. Positive ion mode APPI-MS indicated the exact presence of 39 specific oligomeric ions. Negative ion APPI-MS indicated the additional presence of at least 18 specific oligomeric ions. The structural characterization of this novel and complete series of 57 specific related oligomers was achieved by calculating the exact molecular masses measured by high-resolution quadrupole time-of-flight mass spectrometry (QqToF-MS). Some oligomeric species photoionized in both the positive and negative ion modes to form the respective protonated and deprotonated molecules. Low-energy collision-induced dissociation tandem mass spectrometric analyses performed with a QqToF-MS/MS hybrid instrument provided unique dissociation patterns of the complete series of novel precursor ions. These MS/MS analyses provided diagnostic product ions, which enabled us to determine the exact molecular structures and arrangement of the selected 57 different related ionic species.

Organosolv Wheat Straw Lignin as a Phenol Substitute for Green Phenolic Resins

“…The structure of wheat straw BL has been widely studied (Banoub and Delmas 2003;Banoub et al 2007Banoub et al , 2015Delmas et al 2011a). A model of the structure is proposed in Fig.…”

“…Moreover, the reactivity of the free sites of BL may differ from those of phenol free sites, due to steric hindrance and intrinsic chemical structure (Banoub et al 2007). Both the consumption of formaldehyde in a BL and phenol media and the optimal initial ratio of formaldehyde were evaluated.…”

“…The selected lignin was extracted from wheat straw using a mixture of acetic and formic acids, according to the organosolv pretreatment developed by CIMV (Paris, France) (Delmas and Avignon 2000;Delmas 2008;Delmas et al 2009). Its high purity, low molecular weight, high hydroxyl groups content, and especially its linear fragments make this lignin unique and particularly interesting for this application (Banoub and Delmas 2003;Banoub et al 2007Banoub et al , 2015. In addition to its qualities, this particular lignin, named Biolignin TM , is valuable since CIMV is building its first pre-industrial demonstration plant as part of the European project 2G-BIOPIC (Horizon 2020, Grant Agreement n°657867).…”

Getting Closer to Absolute Molar Masses of Technical Lignins

“…ESI‐MS also has some inherent problems to grasp lignin as a whole: the analyte cannot be ionized uniformly owing to its rather heterogeneous chemical nature so that usually only smaller fragments are detected, and larger molecules are suppressed. Furthermore, the correct assignment of the detected fraction is still a major challenge if it has just to rely on mass spectra without getting additional input from complementary methods, such as nuclear magnetic resonance (NMR) spectroscopy 18, 19…”

Flocculation Performance of Trimethyl Quaternary Ammonium Salt of Lignin-Sodium Alginate Polyampholyte

“…In this context, lignin, which is the second most abundant polymer in nature after cellulose, appears as a promising candidate. Lignin (Banoub et al 2007;Doherty et al 2011) is an amorphous, highly branched polyphenolic macromolecule of complex structure.…”