Benchmarking Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Against Conventional Methods for the Characterization of Solvent-Fractionated Kraft Lignin

Lignins are heterogeneous aromatic biopolymers whose structural complexity depends strongly on botanical origin and isolation process. Comprehensive characterization therefore typically relies on multiple complementary techniques, including gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and nuclear magnetic resonance (NMR) spectroscopy, resulting in labor-intensive workflows and complex data integration. Here, ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is systematically benchmarked against these established methods using solvent-fractionated spruce kraft lignin as a model system. Complementary electrospray ionization (ESI) and graphite-assisted laser desorption/ionization (GALDI), combined with tandem mass spectrometry (MS/MS) and heterospectroscopic correlation analysis, reproduce fraction-dependent trends in oxygenation, aromatic condensation, and functional group distribution consistent with FT-IR, Py-GC/MS, and quantitative NMR data. While limitations remain for molar mass distributions and linkage quantification, FT-ICR-MS can serve as an advanced, high-throughput complementary screening platform that enables streamlined, comparative molecular-level lignin profiling with reduced analytical complexity.