Optimization and Testing of an SPE-LC/q-TOF Analytical Method for the Detection of PFAS Degradation Products in Water Treatment Processes

The research on novel methods for water treatment to achieve the degradation of perfluoroalkyl and polyfluoroalkyl substances (PFAS) is very active and usually considers perfluorooctanoic acid (PFOA) and perfluorooctansulfonic acid (PFOS) to test the process efficacy. Their degradation generally proceeds through the sequential formation of shorter-chain perfluoroalkyl carboxylic acids (PFCAs), which are detected and quantified by means of well-established methods. However, hydro- and hydroxy-defluorinated products of various chain length, in which one or more -F atoms have been substituted by -H atoms and/or -OH groups, can be formed as well. An analytical method was therefore developed, capable of concentrating and simultaneously analyzing PFCAs and these substitution products. Solid-phase extraction and LC-ESI/q-TOF parameters have been optimized to maximize recovery and detection of PFOS, PFOA, shorter-chain PFCAs, and various polyfluoroalkyl and polyfluorohydroxyalkyl carboxylic/sulfonic acids obtained in the treatment of solutions 1.0 × 10^-6 M PFOA or PFOS in tap water by nonthermal plasma (NTP). The application of the developed analytical method, which was tested on real groundwater samples contaminated with PFAS and treated with NTP, is suggested for studies dealing with advanced reduction/oxidation processes for PFAS removal to verify the absence of polyfluoroalkyl and polyfluorohydroxyalkyl carboxylic/sulfonic acids.