Total and Class-Specific Determination of Fluorinated Compounds in Consumer and Food Packaging Samples Using Fluorine-19 Solid-State Nuclear Magnetic Resonance Spectroscopy

By Mike Thijs, Ernest Laletas, Caitlin M. Quinn, Subbu V. Raguraman, Bryan Carr, and Patric Bierganns
Anal Chem
May 8, 2024
DOI: 10.1021/acs.analchem.3c04404

Hamburger wrapping paper, coated with water-based barrier coatings, used in the food packaging industry was studied by using the total organic fluorine (TOF) method based on combustion ion chromatography and fluorine-19 solid-state nuclear magnetic resonance (¹⁹F ss-NMR) spectroscopy. Although the TOF method is a fast and affordable method used to screen for per- and polyfluoroalkyl substances (PFAS), the amount of fluorine it measures is heavily dependent on the extraction step and, therefore could lead to inaccurate results. Fluorine-19 ss-NMR spectroscopy can differentiate between organic and inorganic fluorinated sources, eliminating the need for sample clean up. To illustrate this, the ¹⁹F ss-NMR spectra of clean coated paper samples that contained naturally occurring F^- ions from the talc raw material and spiked samples containing perfluorooctanoic acid were compared. A range of experimental conditions was explored to improve sensitivity for low PFAS concentrations (in the order of 10-20 mg/kg). Despite the disadvantages of ss-NMR spectroscopy, such as the low limit of detection and resolution, the results demonstrate it can be a viable tool to directly detect PFAS moieties in consumer and food packaging. Therefore, ¹⁹F solid-state NMR spectroscopy challenges and complements current methods, which only provide indirect evidence of the presence of PFAS.

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