Fluorine Determinations using the Liquid Sampling - Atmospheric Pressure Glow Discharge / Orbitrap Coupling

Fluoride determinations are crucial across multiple disciplines, including environmental monitoring, drinking water analysis, and nuclear forensics. In PFAS studies, an area of increasing environmental concern, measurement of fluoride anions enables estimation of total fluorine content. While community water fluoridation has been shown to reduce cavity rates by 27%, excessive exposure can lead to health issues such as dental and skeletal fluorosis. In nuclear forensics, fluoride analysis provides the means to date UO₂F₂ particles formed by the reaction of uranium hexafluoride (UF₆) with atmospheric moisture, thereby informing contamination timelines. Conventional fluoride detection techniques, such, inductively coupled plasma–mass spectrometry (ICP-MS), molecular absorption spectroscopy (MAS), and fluorescence spectroscopy, though effective, often require complex sample preparation, derivatization, or face challenges including poor sensitivity in negative ion mode, isobaric interferences, and limited detection limits in the case of ICP-MS. Here, we demonstrate a novel approach employing the liquid sampling–atmospheric pressure glow discharge (LS-APGD) coupled with Orbitrap mass spectrometry to generate high-resolution spectra of fluoride-containing complexes from simple salt solutions. Because F⁻ lies below the Orbitrap’s direct detection range, the analysis is targeted towards fluorine-containing complexes such as oxyanions, which were simplified through optimization of CID, HCD, and plasma conditions. Method validation established response curves, reproducibility, and matrix effects, while mass resolution values of ≥70,000 achieved with the Orbitrap and FTMS Booster X2T enabled differentiation of isobaric interferences. This work introduces a sensitive, high-resolution strategy for the detection of fluorine in its anionic form.