Analysis of Food Contact Paper by Hydrolysis and ¹⁹F-NMR

Food contact paper (FCP) often has polymer treatments applied for grease- and water-resistance. These polymer food contact substances (FCS) are a potential source of dietary exposures to per- and polyfluoroalkyl substances (PFAS). Due to potential health risks associated with exposure to the 6:2 fluorotelomer alcohol (6:2 FTOH), manufacturers committed to phase-out select grease-proofing agents that contain this short-chain PFAS as an impurity in the FCS. This phase-out occurred over a 3-year period which concluded at the end of December 2023. Methods to characterize the fluorine and monitor this phase-out were needed. Prior methodologies employ a hydrolysis step to separate the side-chains and facilitate detection. Fluorine-19 nuclear magnetic resonance spectroscopy (¹⁹F NMR) offers many benefits, both as a monitoring technique and as a tool to assess the reaction. Liquid- and solid-state magic angle spinning (MAS) ¹⁹F NMR were used to examine the fluorine content in FCP coated with polymers containing 6:2 FTOH. Hydrolysis facilitated the analysis of the 6:2 FTOH by releasing it from the polymer FCS. Solid-state NMR offered information regarding fluorine content before and after hydrolysis that when combined with the liquid-state analysis allows the assessment of the reaction. Deuterated sodium hydroxide at a 1 M concentration was sufficient to release most of the FTOH from the majority of the FCP samples. The hydrolysis protocol combined with liquid- and solid-state NMR proved to be an efficient tool to comprehensively examine the fluorine content present in FCS and will be useful as the market surveillance continues past the phase-out period.