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

## TL;DR

This paper develops and tests a new analytical method to detect PFAS degradation products in water treated with nonthermal plasma.

## Contribution

A novel SPE-LC/q-TOF method is optimized for detecting both PFCAs and fluorinated substitution products in water treatment.

## Key findings

- The method successfully detects PFOS, PFOA, and shorter-chain PFCAs in treated water.
- Hydro- and hydroxy-defluorinated products were identified in NTP-treated PFAS solutions.
- The method was validated using real groundwater samples contaminated with PFAS.

## Abstract

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.