Weak Anion-Exchange Chromatography Coupled with FT-ICR MS Resolves Polarity-Driven Molecular Signatures in Natural and Anthropogenic Dissolved Organic Matter

Water-soluble emerging contaminants from fossil fuel-based materials pose increasing environmental risks, yet their detailed molecular characterization remains limited. These compounds often resemble natural dissolved organic matter (DOM), especially after photo-oxidation, which increases oxygen content and structural complexity. We developed a high-performance liquid chromatography (HPLC) method coupled to 21 T Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to enhance molecular analysis of both natural and anthropogenic DOM. The method incorporates a polymeric stationary phase functionalized with amine groups to promote interactions with carboxylic and phenolic moieties. A methanol-to-water gradient containing 2% diethylamine (DEA) promotes separation based on differences in hydrophilicity and functional group interactions with the stationary phase. Compared with direct infusion (DI), the HPLC-FT-ICR MS workflow mitigates ion suppression, enhances ionization efficiency, and broadens molecular coverage. For example, analysis of coal tar-derived water solubles yielded over 16,000 assigned formulas, twice as many as in DI-MS, including oxygen-containing polycyclic aromatic hydrocarbons (oxy-PAHs) and high H/C species poorly ionized under DI conditions. This method achieves efficient separation of chemically diverse compound classes, enabling ultrahigh-resolution MS analysis of complex environmental mixtures and advancing molecular-level understanding of both natural DOM and fossil fuel-derived contaminants.