qNMR fluorine pollution analysis: perspectives on PFAS exposure characterisation using 19F NMR

The presence of anthropogenic fluorinated pollutants in the environment, particularly per- and polyfluoroalkyl substances (PFAS), is an increasing concern. The need for untargeted analytical methods is becoming increasingly critical to comprehensively assess environmental contamination. Classical approaches include targeted searches for marker molecules, for which standard references must be available or total fluorine estimation without individual species identification. Given the diversity of commercially compounds, and their possible degradation products, it appears impossible to obtain a global view of environmental fluorinated species. We present investigation to highlight the potential of liquid state 19F‐Nuclear Magnetic Resonance (NMR) using broadband acquisition and advocate it as a complementary untargeted routine strategy for obtaining additional information alongside existing methods. We introduce a repertoire of 1D and 2D NMR experiments allowing to quantify efficiently all detected fluorinated molecules in a given matrix. The specific problems of 19F-NMR at high magnetic field are exposed, notably the difficulty of exciting and detecting a large broadband spectral width tackled thanks to adapted pulse sequences. Acquisition parameters have been optimized for quantification accuracy and robustness of the proposed techniques against miss-calibration. Despite limited sensitivity compared to others approaches, 19F-NMR insures minimal sample treatment and few handling constraints. Through real-world case studies from consumer products to PFAS-contaminated environments, we demonstrate that 19F-NMR is not only suitable for quantification, but a powerful tool for the comprehensive detection of both known and unexpected fluorinated species in environmental samples, with for instance LOD down to 20 µg/L for trifluoroacetic acid (TFA).