Surface-Enhanced Raman Spectroscopy Detection of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foams

Identifying the presence and identity of per- and polyfluoroalkyl substances (PFAS) in complex mixtures is critical for water treatment, hazardous waste cleanup, and the identification of workplace hazards. The cost and scale of conventional methods for PFAS detection often make rapid and portable detection challenging. Here, we use concave cubic gold nanoparticles for surface-enhanced Raman spectroscopy (SERS) to detect PFAS in parts per million concentrations, differentiating the 6 PFAS─PFHpA, PFNA, PFDA, PFOA, PFHxS, and PFOS─regulated in the Commonwealth of Massachusetts by the Department of Environmental Protection (MassDEP). Calculated Raman spectra, solid-state Raman spectra, and 19F NMR are used to further understand the physicochemical properties of these 6 PFAS. Quantitative analysis of PFOA and PFOS can be achieved from 0.1 to 10 ppm, while PFAS can be differentiated from three common fluorinated pharmaceuticals, and perfluoroalkyl carboxylic acids (PFCA) can be differentiated from C7 to C10 based on the length of the perfluoroalkyl backbone. Finally, we highlight that SERS can be used to identify PFAS in real-world aqueous film-forming foams (AFFFs), as confirmed separately by mass spectrometry. These results advance our ability to detect and analyze PFAS in real-world samples relevant to environmental monitoring and analysis.