Lignin, is produced as a waste product of the paper industry and has potential as a sustainable resource of renewable chemicals. Due to the variety of feedstocks and processing methods and the heteropolymeric character of lignin and its derived products,’ the characterization is challenging even in regards to molecular weight determination. Size exclusion chromatography (SEC) may be affected by unwanted analyte-column interactions due to the broad scope of functionalities in lignin. MALDI MS provides negatively affected by partial fragmentation and limited to a single charge formation. In the present study, we have focused on assessing electrospray high-resolution mass spectrometry (ESI-HR-MS) method to determine the number and average molecular weight and its comparison to previously validated SEC analysis. ESI-HR-MS conditions were optimized considering the broad range of electrolytes taking into account the formation of multiple charged species. Formic and acetic acids were preferred electrolytes using positive ESI, enabling detection of all compounds, i.e., species with prevalent methoxy groups and no hydroxy groups. Some of the standards, effectively ionized in the positive mode, could not be detected in the negative ESI. Applying the developed positive ESI-HR-MS method to a broad range of technical lignins provided comparable data to those obtained with SEC.

Molecular weight determination of technical lignins with electrospray high-resolution mass spectrometry

ACS Spring 2022

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