Will various interpretation strategies of the same ultrahigh‐resolution mass spectrometry data tell different biogeochemical stories? A first assessment based on natural aquatic dissolved organic matter

Abstract

AbstractFourier ion cyclotron resonance mass spectrometry (FT‐ICR MS), one of the state‐of‐the‐art ultrahigh‐resolution techniques, is widely used in dissolved organic matter (DOM) research. As research that focuses on identifying DOM molecular fingerprints increases tremendously, there is and will be an urgent need to compare among studies. Different research groups usually use various types of data processing and interpretation strategies. It is critical to explore if different interpretation strategies will impact the comparability of FT‐ICR MS results and their biogeochemical interpretations. To address this question, we selected DOM samples along a freshwater‐to‐marine continuum to be measured by negative‐ion mode electrospray ionization FT‐ICR MS. We interpreted the raw MS data using different strategies, compared the results and evaluated the interpretation strategy‐induced effects on biogeochemical interpretations. Our results show that a total of 3827 formulas that account for 91.6% ± 4.1% (on average) of the total intensity are assigned in all interpretation strategies, while 6521 formulas for 8.4% ± 4.1% (on average) of the total intensity are not commonly assigned in all three interpretation strategies. We conclude that (i) different interpretation strategies do not significantly affect the geochemical stories relied on DOM molecular composition, and (ii) comparison based on intensity results gives more reliable results than the formular number alone. Moreover, we also provide raw and interpreted data (by our different strategies) for the community to compare their interpretation. We aim to call attention to the community for improving the comparability of FT‐ICR MS results and facilitating the integration of DOM molecular composition among global studies.