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Per-and polyfluoroalkyl substances (PFASs) have been manufactured and used for decades. The aquatic envi-ronment is a critical transportation and transformation compartment for PFASs. Target analysis is the most used method of tracing PFASs in the aquatic environment but is powerless for the large amounts of unknown PFASs. This review summarizes the advantages of three target analysis supplementary approaches, including extractable organofluorine (EOF) analysis, high-resolution mass spectrometry (HRMS) screening, and PFAS precursor oxidative conversion. For known PFASs, more targets, including emerging PFASs, PFAS isomers, ultrashort-chain PFASs, and cationic/zwitterionic PFASs, should be considered. For unknown PFASs and organofluorines, developing comprehensive and low-contaminated sample treatment strategies is essential yet challenging. We propose including PFASs screened via HRMS at confidence level (CL) 3 and above in EOF mass balance analysis and CL 4 for samples collected from a "known source". Appropriate approaches should be applied to investigate unknown PFASs beyond target analysis comprehensively., The present work was supported by the National Key Research and Development Program of China (2022YFC3204800) , Guangdong Basic and Applied Basic Research Foundation (2021A1515012048) , Hong Kong Special Administrative Region, Environment and Conservation Fund (ECF 2021-45) , Science, Technology, and Innovation Commission of Shenzhen Municipality (JCYJ20190812155805559) , and Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (311020004) . This work was also supported by the Innovation and Technology Commission (ITC) of the Hong Kong SAR Government (9448002) which provides regular research funding to the State Key Laboratory of Marine Pollution. However, any opinions, findings, conclusions, or recommendations expressed in this publication do not reflect the views of the Hong Kong SAR Government or the ITC.

Research on per- and polyfluoroalkyl substances (PFAS) frequently incorporates organofluorine measurements, particularly because they could support a class-based approach to regulation. However, standardized methods for organofluorine analysis in a broad suite of matrices are currently unavailable, including a method for extractable organofluorine (EOF) measured using combustion ion chromatography (CIC). Here, we report the results of an international interlaboratory comparison. Seven laboratories representing academia, government, and the private sector measured paired EOF and PFAS concentrations in groundwater and eel (Anguilla rostrata) from a site contaminated by aqueous film-forming foam. Among all laboratories, targeted PFAS could not explain all EOF in groundwater but accounted for most EOF in eel. EOF results from all laboratories for at least one replicate extract fell within one standard deviation of the interlaboratory mean for groundwater and five out of seven laboratories for eel. PFAS spike mixture recoveries for EOF measurements in groundwater and eel were close to the criterion (±30%) for standardized targeted PFAS methods. Instrumental operation of the CIC such as replicate sample injections was a major source of measurement uncertainty. Blank contamination and incomplete inorganic fluorine removal may introduce additional uncertainties. To elucidate the presence of unknown organofluorine using paired EOF and PFAS measurements, we recommend that analysts carefully consider confounding methodological uncertainties such as differences in precision between measurements, data processing steps such as blank subtraction and replicate analyses, and the relative recoveries of PFAS and other fluorine compounds., Funding Agency:National Institute for Environmental Health Sciences (NIEHS) Superfund Research Program P42ES027706 P42ES031009

The ban/elimination of legacy per- and polyfluoroalkyl substances (PFASs) has led to a dramatic increase in the production and use of various emerging PFASs over the past decade. However, trophodynamics of many emerging PFASs in aquatic food webs remain poorly understood. In this study, samples of seawaters and marine organisms including 15 fish species, 21 crustacean species, and two cetacean species were collected from the northern South China Sea (SCS) to investigate the trophic biomagnification potential of legacy and emerging PFASs. Bis(trifluoromethylsulfonyl)imide was found in seawater via suspect screening (concentration up to 1.50 ng/L) but not in the biota, indicating its negligible bioaccumulation potential. A chlorinated perfluorooctane sulfonate (PFOS) analytical interfering compound was identified with a predicted formula of C14H23O5SCl6- (most abundant at m/z = 514.9373). Significant trophic magnification was observed for 22 PFASs, and the trophic magnification factors of cis- and trans-perfluoroethylcyclohexane sulfonate isomers (1.92 and 2.25, respectively) were reported for the first time. Perfluorohexanoic acid was trophic-magnified, possibly attributed to the PFAS precursor degradation. The hazard index of PFOS was close to 1, implying a potential human health risk via dietary exposure to PFASs in seafood on the premise of continuous PFAS discharge to the SCS., Funding agencies:National Key Research and Development Program of China 2022YFC3204800Guangdong Basic and Applied Basic Research Foundation 2021A1515012048Theme-Based Research Scheme of Research Grants Council of the Hong Kong SAR Government T21-602/16-RInnovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) 311020004Innovation and Technology Commission (ITC) of the Hong Kong SAR Government 9448002State Key Laboratory of Marine Pollution