Analytical Development for Detecting Femtomole-Level Organophosphorus Compounds in Biogeochemical Samples by Ion Chromatography/High-Resolution Mass Spectrometry

Phosphorus (P) is a crucial element for life, and its organic forms play a central role in modern biology. Therefore, the analysis of their presence in environmental samples is important for evaluating the biogeochemistry of P and the P cycle on the Earth. Herein, we developed a high-sensitivity, high-resolution analytical technique for detecting organophosphorus compounds using ion chromatography (IC) with Orbitrap-mass spectrometry (Orbitrap-MS). The IC method clearly separated organophosphorus compounds, including alkyl phosphonates and alkyl phosphates, from other organic molecules and inorganic ions. The online combination of IC and Orbitrap-MS enabled the quantification of organophosphorus compounds with concentrations as low as ∼10 fmol and their molecular identification in the presence of various interfering organic substances. The feasibility of the developed and optimized IC-Orbitrap-MS method was confirmed by analyzing deep-sea sediments obtained from 343 m below the seafloor. This developed analytical technique can also be applied to biogeochemical and astrochemical molecular surveys of organophosphorus compounds in natural environments.