Advancing PFAS characterization: Enhancing the total oxidizable precursor assay with improved sample processing and UV activation

David Patch; Natalia O'Connor; Taylor Vereecken; Daniel Murphy; Gabriel Munoz; Ian Ross; Caitlin Glover; Jennifer Scott; Iris Koch; Sébastien Sauvé; Jinxia Liu; Kela Weber

doi:10.1016/j.scitotenv.2023.168145

Advancing PFAS characterization: Enhancing the total oxidizable precursor assay with improved sample processing and UV activation

Sci Total Environ. 2024 Jan 20:909:168145. doi: 10.1016/j.scitotenv.2023.168145. Epub 2023 Nov 11.

Authors

Affiliations

¹ Environmental Sciences Group, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON K7K 7B4, Canada.
² Brace Water Center, Department of Civil Engineering, McGill University, Montreal, QB H3A 0G4, Canada.
³ CDM Smith, 75 State St #701, Boston, MA 02109, United States of America.
⁴ Département de chimie, Université de Montréal, Montréal, QC H2V 0B3, Canada.
⁵ Environmental Sciences Group, Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, ON K7K 7B4, Canada. Electronic address: Kela.Weber@rmc.ca.

PMID: 37952659
DOI: 10.1016/j.scitotenv.2023.168145

Abstract

Per- and polyfluoroalkyl substances (PFAS) encompass over 9000 chemicals utilized in various industrial and commercial applications. However, the quantification of PFAS using standard commercial analytical methods is currently limited to <50 selected compounds. To address this issue, the total oxidizable precursor (TOP) assay was developed, allowing for the oxidative conversion of previously undetectable PFAS precursors into measurable PFAS. This study investigated different sample processing methods to address post-oxidation PFAS loss identified in literature. Using PFOS as a probe molecule, up to 50 % loss of PFOS was identified during sample work-up. It was determined that the use of mass-labelled PFOS and methanolic acetic acid to chemically quench the sample post-oxidation improved PFOS recovery and allowed for correction of any remaining PFOS loss. The use of ultraviolet (UV) light was then investigated as an activator in contrast to the standard thermal activation method. A comparative evaluation was conducted to assess the recovery and conversion of perfluorooctanoic acid (PFOA), PFOS, and 6:2 fluorotelomer sulfonate (6:2 FTS) using both the heat-activated and UV-activated TOP assays. Results demonstrated that the UV-activated TOP assay achieved complete (100 %) oxidation of 6:2 FTS within 7.5 min, resulting in a total yield of generated perfluorinated carboxylic acids (PFCAs) at 108 ± 8 %. The study concluded by investigating the UV-activated TOP assay for its application on various aqueous film forming foam (AFFF) formulations and two AFFF samples drained from military aircraft rescue firefighting vehicles (ARFFVs). Analysis of these AFFF samples were supported by high resolution mass spectrometry and an expanded analytical suite, identifying several fluorotelomer precursors. The findings of this study provide compelling evidence that modifications in sample processing, work-up procedures, expansion of initial PFAS calibration standards, and UV-activation methods enhance the TOP assay, positioning it as a more reliable and quantitative analytical tool for PFAS characterization.

Keywords: 6:2 FTS; AFFF; Analysis; PFOA; PFOS; TOP assay.