Generic Method for the Detection of Short & Long Chain PFAS Extended to the Lowest Concentration Levels of SERS Capability

Abstract

The detection of the highly toxic perfluoroalkyl substances, PFAS, constitutes a challenging task in terms of developing a generic method that could be rapid and applicable simultaneously to both long and short-chain PFAS at ppt concentration level. In the present study, the method introduced by the USA Environmental Protection Agency to detect surfactants, or methylene blue active substances, is extended at the lowest concentration range by a simple additional step that involves the dissociation of the ion pairs in water. In this work, Surface Enhanced Raman Scattering, SERS, is applied via Ag nanocolloidal suspensions to probe methylene blue and indirectly either/or both short-chain (perfluorobutyric acid, PFBA) and long-chain (perfluoloctanoic acid, PFOA) PFAS in the range of 5 ppt. This method, which can be further optimized to sub-ppt level via a custom-made SERS-PFAS dedicated Raman system, offers the possibility to be applied to either specific PFAS (both short and long-chain) in a targeted analysis or to total PFAS in a non-targeted analysis at very low detection limits, following any type of methylene blue detection method in aqueous solutions and obviously with any type of SERS substrate.

Keywords: Perlyfluorinated substances (PFAS), Surface Enhanced Raman Scattering (SERS), ion pairing