Trifluoroacetic acid (TFA) in grain products from the US supermarkets

A targeted analytical method for seven short- and ultra-short chain per- and polyfluoroalkyl substances (PFAS) was developed and validated in grain products using LC-MS/MS. The method is simple and robust, with validation results demonstrating acceptable recoveries and reproducibility. The validated method was applied to a variety of grain products commonly consumed in the United States, including flour, rice, corn, oats, and pasta, with both conventional and organic products represented. Trifluoroacetic acid (TFA) was detected in 92 out of 95 samples with concentrations ranging from not detectable to 356 ng/g. To evaluate the impact of cooking, selected grains were prepared according to typical household practices and analysed alongside the corresponding cooking water. TFA concentrations generally decreased after cooking, accompanied by transfer into the cooking water. Among all tested grain products, flour contained the highest TFA levels (range: 36.6-356 ng/g), followed by oats (27.5-292 ng/g), pasta (13.6-265 ng/g), and rice (8.52-77.8 ng/g). Historical grain samples collected between 2016 and 2019 were also analysed, providing a retrospective view of TFA occurrence, and analysis of identical products purchased in 2026 indicated an overall upward trend in TFA levels. Estimated dietary intake of TFA from cooked grains was below the European Food Safety Authority's (EFSA) acceptable daily intake of 0.014 mg/kg body weight.