A comparative study of the electrospray ionization response of β‐O‐4′ lignin model compounds

Abstract

Electrospray ionization mass spectrometry has recently become the technique of choice for rapid characterization of lignin degradation products. However, the fundamental question of the relationship between lignin structure and ionization efficiency has not been explored. In this work, we studied the electrospray ionization response of five structurally similar β‐O‐4′ model lignin compounds using lithium cationization in the positive electrospray ionization mode. The studied compounds have the same β‐O‐4′ backbone structure but differ at the α‐position by increasing nonpolar side chains. Our results show a correlation between the ionization response and the length of the nonpolar side chain, with analytes having the longest side chain recording the highest ESI response in the full scan mode. Factors affecting the formation of analyte ions and analyte cluster ions were also studied. We have shown for the first time in this work that the introduction of a nonpolar group onto a β‐O‐4′ lignin compound can increase the lithium cationization ESI response in the positive ion mode.

Top–down lignomics analysis of the French oak lignin by atmospheric pressure photoionization and electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry: Identification of a novel series of lignans

“…Recently, a major effort was directed to comprehend whether the ion intensity in an ESI‐MS spectrum actually reflects the measured lignin solution concentrations or not. This was needed in order to avoid problems in the analytical quantification of lignin 40 …”

“…This was needed in order to avoid problems in the analytical quantification of lignin. 40 S C H E M E 1 0 Low-energy CID-MS/MS fragmentation mechanism of the protonated precursor ion 10 at m/z 471.13…”

Mass spectrometry‐based methods for the advanced characterization and structural analysis of lignin: A review

“…This is of high relevance for lignin, as larger LOs are otherwise disintegrated in other methods (i.e., EI, MALDI). ESI is therefore an ideal ionization method for the analysis of lignin by MS. For example, a recent study used well‐characterized β‐ O ‐4′ lignin model compounds to optimize several parameters of their ESI setup, including ionization mode (positive or negative), addition of lithium, addition of polar aprotic “supercharging” solvents (modifiers) such as dimethyl sulfoxide and dimethylformamide and the role of nonpolar groups in affecting ionization response (Asare & Lynn, 2019). Their optimized method involved adding a nonpolar group onto a β‐ O ‐4′ lignin compound, increasing the lithium cationization ESI response in positive ion mode.…”

Standard-Free Quantification of Dicarboxylic Acids: Case Studies with Salt-Rich Effluents and Serum

“…Several studies were performed to find the relationship between ionization efficiency and molecular properties. The positive correlations between the ionization efficiency and octanol/water partition coefficient (LogP) values for sartans (angiotensin-II-receptor antagonists) and phenolic compounds, the length of the nonpolar side chains for lignin model compounds, retention times, and nonpolar surface areas for small peptides were observed. − …”