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Assessing contribution of PFCA precursor compounds to total organofluorine compounds from firefighting foam samples using the total oxidizable precursor (TOP) assay on hydroxyl radical-mediated reactions
Örebro University, School of Science and Technology.
2017 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

Per- and polyfluoroalkyl substances (PFASs) are used in many different commercial products, such as cosmetics, plastics, and firefighting foams, and as surfactants or surface protectors. During the last decades, the interest for PFASs has increased because several studies had shown detection of PFASs in the environment, wildlife, and in humans. One of the known sources of contamination from PFASs in the environment comes from aqueous film-forming foam (AFFF). The fluorinated compounds mostly used in AFFFs are 6:2 fluorotelomer-based compounds which can degrade to persistent perfluorinated carboxylic acids (PFCAs).

The aim of this study was to assess the contribution of PFCA precursor compounds in AFFFs using the total oxidizable precursor (TOP) assay, which uses hydroxyl radicals to transform precursors of perfluoroalkane sulfonates (PFSAs) and PFCAs to measurable PFCAs; whereas total organofluorine (TOF) analysis was also conducted to evaluate the presence of any unidentified PFAS in the foam samples.

The results based on the measurement from liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) without any oxidative conversion showed that foam concentrate 1 (Sthamex) mostly consisted of 6:2 fluorotelomer sulfonic acid (FTSA), although 4:2 FTSA and 8:2 FTSA were also detected. Two different PFCAs, perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA) were also detected in Sthamex. In foam concentrate 2 (ArC), 6:2 FTSA and PFHxA were detected. After the two foam samples had been subjected to oxidative conversion, the predominant compounds were C4 to C7 PFCAs, with a molar ratio of 30:54:7:1 for C4:C5:C6:C7 for concentrate 1 and 36:65:11:1 for concentrate 2. For both foam concentrates, long-chain PFCAs ( C8) were detected. The TOF results showed that the unidentified PFAS compounds transformed from neutral/cationic compounds to anionic compounds after oxidation. The mass balance of detected PFASs and the TOF concentrations showed that there still were quite high levels of unidentified PFASs in the samples.

Place, publisher, year, edition, pages
2017. , p. 27
Keywords [en]
Per- and polyfluoroalkyl substances, AFFFs, combustion ion chromatography, persulfate oxidation
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:oru:diva-64646OAI: oai:DiVA.org:oru-64646DiVA, id: diva2:1178605
Subject / course
Chemistry
Supervisors
Examiners
Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2018-01-30Bibliographically approved

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  • apa
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