Closing the gap – inclusion of ultrashort-chain perfluoroalkyl carboxylic acids in the total oxidizable precursor (TOP) assay protocol

Abstract

A novel selective solid–liquid extraction of PFASs from oxidized batches of the total oxidizable precursor (TOP) assay enables a complete mass balance by inclusion of ultrashort-chain PFASs.

Challenges in the analytical determination of ultra-short-chain perfluoroalkyl acids and implications for environmental and human health

“…Two recent studies reported low recovery of ultra-shortchain PFAAs in samples after chemical oxidation at high pH using persulfate and sodium hydroxide (i.e., total oxidizable precursor (TOP) assay) [29,30]. The TOP assay results in a solution containing large amounts of SO 4 2− and the pH is around 10; before SPE, the pH has to be adjusted to 4 using HCl.…”

“…Therefore, due to the persistence of TFA and other ultra-short-chain PFAAs, along with expected increased environmental concentrations, continued attention is necessary. Furthermore, there has been an increasing interest on methods for TOP assay and extractable organic fluorine with the inclusion of ultra-short-chain PFAAs, since they can be formed as oxidation products and will contribute to the fluorine mass balance [29,30]. Efforts should be made to increase the performance of the existing methods, in terms of extraction recovery, repeatability, and reproducibility, so that produced data can be comparable.…”

“…Extraction of PFASs including ultra-short-chain PFAAs from water is commonly done using a method based on mixed-mode hydrophobic and weak anion-exchange solidphase extraction (WAX-SPE) [20]. However, recent studies report varying and matrix depending extraction recoveries for TFA [11,28], and work has focused on increasing the recovery of ultra-short-chain PFAAs in complex sample matrices [29,30]. Several reviews on PFAS summarizing the current state of knowledge and the existing analytical techniques exist; however, there are no published reviews addressing neither the challenge in the analytical determination of ultrashort-chain PFAAs nor their sources, environmental fate, occurrence, and implications.…”

Biomagnification of perfluoroalkyl acids (PFAAs) in the food web of an urban river: assessment of the trophic transfer of targeted and unknown precursors and implications

“…To get further insight into the bioaccumulation of organic fluoride in fish exposed to AFFF formulations, Yeung and Mabury 47 implemented a mass balance analysis based on the determination of both total fluorine (TF) and extractable organic fluorine (EOF) in fish tissues. They demonstrated that known PFASs explained only 0.9-7% of EOF in unexposed fish and < 7%-60% in exposed fish.…”

Investigation of per- and polyfluoroalkyl substances (PFAS) in soils and sewage sludges by fluorine K-edge XANES spectroscopy and combustion ion chromatography

“…The ongoing production of new, yet unrestricted, PFAS alternatives has become a major challenge not only for researchers across the planet, but also for environmental routine analytics, since the state-of-the-art method LC-MS/MS relies on structural information and availability of isotope standards of the targeted compound (Nakayama et al 2019). Although establishment of the total oxidizable precursor (TOP) assay protocol significantly improves their analytical range (Houtz and Sedlak 2012;Janda et al 2019), target analytical methods only enable detection of approximately 70 different PFAS, thus will increasingly become a limiting factor (Koch et al 2020). Since the number of PFAS alternatives is also relative to advancing progress of the regulatory enforcement, different future analytical approaches are inevitable.…”