Unwanted ingredients - highly specific and sensitive method for the extraction and quantification of PFAS in everyday foods.

Perfluorinated alkyl substances (PFAS) are anthropogenic substances and can only come from polluted sources. There are many classes of PFAS which can be transformed to perfluoalkyl carboxylic acids (PFCA) and perfluoroalkyl sulfonic acids (PFSA) in the environment. Once they are in this form they are environmentally mobile and extremely stable with half-lives of decades. These compounds are not innocuous and are implicated in causing many different diseases.
High resolution mass spectrometry is an extremely sensitive and specific analytical technique capable of detecting down to ng.g-1 level. The high mass resolution can provide a high degree of confidence of the chemical composition and identity of the analyte, especially when coupled with fragmentation experiments. However regardless of this high mass accuracy quantitation still needs careful consideration as matrix effect can enhance or suppress the signal. Matrix effect is caused by background ions which can adversely affect the target ion signal. Also the ubiquitous nature of PFAS can make analysis more difficult due to their presence in solvents and plastics used in the analytical techniques. In this publication a method for the extraction and quantitation of PFCAs and PFSAs, using high resolution liquid chromatography mass spectrometry (HRMS), is evaluated. A QuEChERS extraction method was performed on tomatoes, strawberries and milk purchased from different supermarkets on different days. Recoveries from milk and tomatoes were between 80 and 120%. Matrix effects were significant for strawberries and tomatoes and stable isotope internal standards were used to compensate. PFBA was found in all 3 food types. The total PFAS was 0.68 ng.g-1 in milk, 0.20 ng.g-1 in strawberries and 0.36 ng.g-1 in tomatoes. This study demonstrates the importance of using a robust analytical method to investigate the PFAS content of complex food matrices and in particular the contribution of short-chain PFAS to overall dietary consumption.