Improved Molecular-Level Profiling of Dissolved Organic Matter through FTICR-MS Based on Multiple ICR Cell Fills

Although Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) has been proven to be a powerful tool for the analysis of dissolved organic matter (DOM), obtaining more comprehensive molecular-level information about DOM remains extremely challenging due to its complexity. In this work, we found that ICR cell fills (ICRCF) have a significant impact on DOM detection using FTICR-MS. A multiple-ICRCF value of 10 is optimal, significantly enhancing peak intensities and the signal-to-noise ratio without inducing spectral artifacts. The multiple-ICRCF method identified more than 2400 additional molecular formulas compared to the single-ICRCF approach, particularly revealing more aromatic and less oxygenated compounds, as well as a substantial number of 13C1-isotopic peaks. The increased formula diversity improved the resolution of molecular profiles and enabled the construction of more complex and informative potential molecular transformation networks. Additionally, multiple ICRCF measurements effectively improved the sensitivity of FTICR-MS for DOM detection. These results demonstrated multiple ICRCF as a powerful supplementary technique for advancing molecular-level characterization of complex DOM, with implications for biogeochemical cycles.