Robust trace analysis of polar (C2-C8) perfluorinated carboxylic acids by liquid chromatography-tandem mass spectrometry: method development and application to surface water, groundwater and drinking water

Occurrence of short- and ultra-short chain PFAS in drinking water from Flanders (Belgium) and implications for human exposure

SHORT: and ultra-short chain perfluoroalkyl substances (S- and US-PFAS) are alternatives for the long-chain PFAS which have been more regulated over time. They are highly mobile in the environment and can easily reach drinking water sources which can become an important human exposure route. Furthermore, there have been growing concerns about the presence of PFAS in Flanders. Because of this, human exposure to S- and US-PFAS through Flemish drinking water was evaluated in this study. For this purpose, the presence of 2 S-PFAS (PFBS and PFBA) and 5 US-PFAS (PFPrS, PFEtS, TFMS, PFPrA and TFA) was investigated in 47 tap water samples, collected from different Flemish provinces, and 16 bottled waters purchased in Flanders. Out of the 7 target PFAS, 4 (PFBA, PFBS, PFPrS and PFEtS) were detected at concentrations above LOQ in tap water. In bottled water, only TFMS was present above its LOQ. PFAS concentrations in all analyzed water samples ranged from <0.7 to 7.3 ng/L for PFBS, <0.03-15.0 ng/L for TFMS and <0.9-12.0 ng/L for PFBA. PFPrS was only detected once above its LOQ, at 0.6 ng/L. No value could be reported for PFPrA due to high procedural blanks resulting in a high LOQ, nor for TFA due to high matrix effect. No significant differences in PFAS concentrations were seen in tap water among different drinking water companies, provinces, nor between the two types of analyzed bottled water (natural mineral water vs spring water). The use of a commercial carbon filter significantly reduced the median concentrations of the studied compounds in tap water. Finally, it was estimated that the presence of S- and US-PFAS in Flemish drinking water does not pose an immediate threat to human health, as concentrations were at least two orders of magnitude below the available guidance values.

Determination of regulated perfluoroalkyl substances (PFAS) in drinking water according to Directive 2020/2184/EU

Perfluoroalkyl substances (PFAS) are chemical compounds that have been widely used in industry and manufacture. Occurrence, together with persistence and recent toxicological effects data, has promoted the regulation of 20 PFAS (carboxylic and sulfonic) acids in drinking water through the recent Directive 2020/2184/EU. This Regulation included PFAS with different carbon chain lengths (from C4 to C13) and limited the total PFAS concentration (as sum) to a maximum of 0.1 µg/L, for which law-enforcement analytical methods are required. In this work, three different methodologies have been developed and evaluated as regards their performance to determine those 20 PFAS in tap and bottled water, based on on-line and off-line solid-phase extraction (SPE) and direct injection. In all cases, ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used as a determination technique. Off-line SPE with Oasis Weak Anion Exchange (WAX) cartridges provided the best results in terms of limits of quantification (LOQ ≤ 0.3 ng/L) and accuracy (R ≥ 70%) in drinking water samples. On-line SPE and direct injection presented some drawbacks such as background contamination problems and lower accuracies for the least polar compounds. This off-line SPE methodology was then applied to the analysis of 46 drinking water samples (11 commercial bottled samples, 23 Spanish and 12 international tap water samples). Ten PFAS were quantified in such samples at concentrations and detection frequencies ranging from 0.1 to 20.1 ng/L and 2 to 91%, respectively. However, the sum concentration did not surpass the established limit in any sample.

Highly sensitive and accurate measurement of underivatized phosphoenolpyruvate in plasma and serum via EDTA-facilitated hydrophilic interaction liquid chromatography-tandem mass spectrometry

Phosphoenolpyruvate (PEP) is an essential intermediate metabolite that is involved in various vital biochemical reactions. However, achieving the direct and accurate quantification of PEP in plasma or serum poses a significant challenge owing to its strong polarity and metal affinity. In this study, a sensitive method for the direct determination of PEP in plasma and serum based on ethylenediaminetetraacetic acid (EDTA)-facilitated hydrophilic interaction liquid chromatography-tandem mass spectrometry was developed. Superior chromatographic retention and peak shapes were achieved using a zwitterionic stationary-phase HILIC column with a metal-inert inner surface. Efficient dechelation of PEP-metal complexes in serum/plasma samples was achieved through the introduction of EDTA, resulting in a significant enhancement of the PEP signal. A PEP isotopically labelled standard was employed as a surrogate analyte for the determination of endogenous PEP, and validation assessments proved the sensitivity, selectivity, and reproducibility of this method. The method was applied to the comparative quantification of PEP in plasma and serum samples from mice and rats, as well as in HepG2 cells, HEK293T cells, and erythrocytes; the results confirmed its applicability in PEP-related biomedical research. The developed method can quantify PEP in diverse biological matrices, providing a feasible opportunity to investigate the role of PEP in relevant biomedical research.

Assessment of legacy and emerging PFAS in the Oder River: Occurrence, distribution, and sources

The purpose of the study was to evaluate the occurrence and distribution of emerging contaminants, poly- and perfluoroalkyl substances (PFAS), in the Polish Oder River, aiming to uncover new insights into their environmental impact. The research aimed to identify potential sources of PFAS, assess water quality levels, and verify compliance with European Union environmental quality standards. The concentrations of 25 PFAS (20 legacy and 5 emerging) in 20 samples from intakes upstream and downstream of urban areas were analyzed using novel, developed in these studies, environmental analytical procedures involving solid phase extraction and liquid chromatography-tandem mass spectrometry. The presence of 14 PFAS was confirmed, and the concentration of Σ14PFAS ranged from 7.6 to 68.0 ng/L. The main components were short-chain analogs. PFBA was the most abundant, accounting for about one-third of all PFAS detected. An exception was observed in the waters of the Gliwice Canal, where ADONA represented half of the detected Σ14PFAS. Alternative PFOS replacements were found in all samples. In 11 of 20 water samples, environmental quality standards for PFOS exceeded the limit of 0.65 ng/L. In 5 of 9 cases, the ability of urban areas to increase PFAS levels in the river was determined. 9.5%-54.4% share of alternative PFAS in relation to the sum of the targeted PFAS showing their increasing use as substitutes for phased-out PFOS. Hierarchical cluster analysis was used to identify potential sources of PFAS. Analysis revealed that PFAS in the Oder River most likely originated from domestic and agricultural wastewater, as well as chemical industry discharges. However, the occurrence of PFAS in the Oder River is low and comparable to other recent European studies. These findings provide valuable insights for environmental management to mitigate the risks associated with PFAS pollution in Polish rivers. Moreover, the developed analytical procedure provides a valuable tool that can be successfully applied by other researchers to monitor PFAS in rivers around the world.

Measurement of perfluoroalkyl substances in drinking water sources by DGT sampler with a novel fluorinated graphite binding gel

Extensive use of per- and polyfluoroalkyl substances (PFASs) has resulted in their widespread presence in natural waters. Concern for public health requires reliable measurement methods for determining their distribution and risks. Here, a sampling method based on diffusive gradients in thin films (DGT) was developed for measuring PFASs in drinking water sources. Fluorinated graphite (FG) particles were used to prepare the DGT binding gel for selective enrichment of trace PFASs in an aqueous environment. The FG-DGT method did not show sensitivity to relevant environmental parameters including pH (5.0-9.0), ionic strength (0.001-0.5 M), or DOM concentration (0-30 mg/L). The FG-DGT had enough capacity for deployment of up to four months. Six traditional and emerging PFASs including PFOS, PFOA, PFHpA, PFHxS, PFNA, and 6:2 FTSA at the ng/L level were detected in two major reservoirs serving as public drinking water sources by FG-DGT method coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS). PFOA appeared at the highest observed concentrations in the drinking water sources. The research demonstrates that FG-DGT is an effective and efficient tool for monitoring PFASs in drinking water.

New PFASs Identified in AFFF Impacted Groundwater by Passive Sampling and Nontarget Analysis

Monitoring contamination from per- and polyfluoroalkyl substances (PFASs) in water systems impacted by aqueous film-forming foams (AFFFs) typically addresses a few known PFAS groups. Given the diversity of PFASs present in AFFFs, current analytical approaches do not comprehensively address the range of PFASs present in these systems. A suspect-screening and nontarget analysis (NTA) approach was developed and applied to identify novel PFASs in groundwater samples contaminated from historic AFFF use. A total of 88 PFASs were identified in both passive samplers and grab samples, and these were dominated by sulfonate derivatives and sulfonamide-derived precursors. Several ultrashort-chain (USC) PFASs (≤C3) were detected, 11 reported for the first time in Australian groundwater. Several transformation products were identified, including perfluoroalkane sulfonamides (FASAs) and perfluoroalkane sulfinates (PFASis). Two new PFASs were reported (((perfluorohexyl)sulfonyl)sulfamic acid; m/z 477.9068 and (E)-1,1,2,2,3,3,4,5,6,7,8,8,8-tridecafluorooct-6-ene-1-sulfonic acid; m/z 424.9482). This study highlights that several PFASs are overlooked using standard target analysis, and therefore, the potential risk from all PFASs present is likely to be underestimated.

Comparison of the photocatalytic degradability of PFOA, PFOS and GenX using Fe-zeolite in water

Knowledge on the photocatalytic degradability of the emerging poly- and perfluorinated alkyl substances (PFAS) in water, specifically GenX, is limited. GenX has been detected globally in river water and is considered potentially more toxic than legacy PFAS. In this study, we compared the photocatalytic degradability of GenX with the legacy compounds perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using Fe-zeolite photocatalysts. After 7 h of irradiation, GenX showed lower removal (79%) and defluorination (33%) as compared to PFOA (100% removal and 69% defluorination) and PFOS (100% removal and 51% defluorination). The quasi-first-order degradation rate of GenX (1.5 h1) was 12 and 1.2 times lower than PFOA (18.4 h-1) and PFOS (1.8 h-1), respectively. Additionally, PFOA's defluorination rate (0.9 h-1) was approximately 2.6 and 9 times higher than GenX (0.35 h-1) and PFOS (0.1 h-1), respectively. These outcomes correlate with GenX's lower hydrophobicity, leading to reduced adsorption (40%) compared to PFOA (99%) and PFOS (87%). Based on identified transformation products, we proposed a GenX degradation pathway, resulting in ultra-short-chain PFASs with a chain length of 2 and 3 carbon atoms, while PFOA and PFOS degraded stepwise, losing 1 carbon-fluorine bond at a time, leading to gradually shorter chain lengths (from 7 to 2 carbon atoms). In conclusion, GenX is more challenging to remove and degrade due to its lower adsorption on the photocatalyst, potential steric hindrance, and higher production of persistent ultra-short-chain transformation products through photocatalysis.

Water, Water Everywhere, but Every Drop Unique: Challenges in the Science to Understand the Role of Contaminants of Emerging Concern in the Management of Drinking Water Supplies

The protection and management of water resources continues to be challenged by multiple and ongoing factors such as shifts in demographic, social, economic, and public health requirements. Physical limitations placed on access to potable supplies include natural and human-caused factors such as aquifer depletion, aging infrastructure, saltwater intrusion, floods, and drought. These factors, although varying in magnitude, spatial extent, and timing, can exacerbate the potential for contaminants of concern (CECs) to be present in sources of drinking water, infrastructure, premise plumbing and associated tap water. This monograph examines how current and emerging scientific efforts and technologies increase our understanding of the range of CECs and drinking water issues facing current and future populations. It is not intended to be read in one sitting, but is instead a starting point for scientists wanting to learn more about the issues surrounding CECs. This text discusses the topical evolution CECs over time (Section 1), improvements in measuring chemical and microbial CECs, through both analysis of concentration and toxicity (Section 2) and modeling CEC exposure and fate (Section 3), forms of treatment effective at removing chemical and microbial CECs (Section 4), and potential for human health impacts from exposure to CECs (Section 5). The paper concludes with how changes to water quantity, both scarcity and surpluses, could affect water quality (Section 6). Taken together, these sections document the past 25 years of CEC research and the regulatory response to these contaminants, the current work to identify and monitor CECs and mitigate exposure, and the challenges facing the future.

The wide presence of fluorinated compounds in common chemical products and the environment: a review

The C-F bonds, due to their many unique features, have been incorporated into numerous compounds in countless products and applications. These fluorinated compounds eventually are disposed of and released into the environment through different pathways. In this review, we analyzed the occurrence of these fluorinated compounds in seven types of products (i.e., refrigerants/propellants, aqueous film-forming foam, cosmetics, food packaging, agrochemicals, pharmaceuticals, coating materials) and discussed their fate in the environment. This is followed by describing the quantity of fluorinated compounds from each source based on available data. Total on- and off-site disposal or other releases of 536 fluorinated compounds in 2021 were analyzed using the data sourced from the U.S. EPA Toxics Release Inventory (TRI). Among the chemicals examined, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) were the primary contributors in terms of total mass. Upon examining the seven sources of fluorinated compounds, it became evident that additional contributors are also responsible for the presence of organofluorine compounds in the environment. Although various toxic degradation products of fluorinated compounds could form in the environment, trifluoroacetic acid (TFA) was specifically highlighted in this review given the fact that it is a common dead-end degradation product of > 1 million chemicals. This paper ended with a discussion of several questions raised from this study. The path forward was elaborated as well for the purpose of protecting the environment and human health.

Rapid Screening and Quantification of PFAS Enabled by SPME-DART-MS

Per- and polyfluoroalkyl substances (PFAS), an emerging class of toxic anthropogenic chemicals persistent in the environment, are currently regulated at the low part-per-trillion level worldwide in drinking water. Quantification and screening of these compounds currently rely primarily on liquid chromatography hyphenated to mass spectrometry (LC-MS). The growing need for quicker and more robust analysis in routine monitoring has been, in many ways, spearheaded by the advent of direct ambient mass spectrometry (AMS) technologies. Direct analysis in real time (DART), a plasma-based ambient ionization technique that permits rapid automated analysis, effectively ionizes a broad range of compounds, including PFAS. This work evaluates the performance of DART-MS for the screening and quantification of PFAS of different chemical classes, employing a central composite design (CCD) to better understand the interactions of DART parameters on their ionization. Furthermore, in-source fragmentation of the model PFAS was investigated based on the DART parameters evaluated. Preconcentration of PFAS from water samples was achieved by solid phase microextraction (SPME), and extracts were analyzed using the optimized DART-MS conditions, which allowed obtaining linear dynamic ranges (LDRs) within 10 and 5000 ng/L and LOQs of 10, 25, and 50 ng/L for all analytes. Instrumental analysis was achieved in less than 20 s per sample.

A Rapid Derivatization for Quantitation of Perfluorinated Carboxylic Acids from Aqueous Matrices by Gas Chromatography-Mass Spectrometry

Ultrashort-chain perfluorinated carboxylic acids (PFCAs) are receiving more attention due to their ever-increasing presence in the environment. Methods have been established for the analysis of short- and long-chain PFCAs, while robust quantitation of ultrashort-chain species is scarce. Here, we develop a novel derivatization method using diphenyl diazomethane for quantitation of C2-C14 PFCAs in aqueous matrices. The method is highlighted by rapid completion of derivatization (<1 min) and retention and separation of ultrashort-chain (C2/C3) PFCA derivatives using H₂ carrier gas (R > 1.5). A weak anion exchange solid-phase extraction procedure for analyte recovery from representative aqueous samples was developed and validated by spike and recovery from ultrapure water, synthetic ocean water, and simulated denuder extracts used for collecting gaseous PFCAs. Recoveries for PFCAs ranged from 83 to 130% for the majority of analytes and matrices. The instrument detection limits (IDLs) range from 8 to 220 fg per injection, and method detection limits (MDLs) range from 0.06 to 14.6 pg/mL for 500 mL aqueous samples, which are within an order of magnitude to conventional LC-MS/MS methods. The method was applied to the analysis of real samples of tap water, rainwater, ocean water, and annular denuder extracts. The overall method provides a cost-effective alternative to conventional LC-MS/MS methods, overcoming the typical GC-MS drawbacks of high detection limits and long sample preparation times while being able to simultaneously analyze the complete spectrum of environmentally relevant PFCAs.

Quantification and characterization of PFASs in suspended particulate matter (SPM) of German rivers using EOF, dTOPA, (non-)target HRMS

In this study, we compare analytical methods for PFAS determination-target analysis, non-target screening (NTS), direct total oxidizable precursor assay (dTOPA) and extractable organically bound fluorine (EOF). Therefore, suspended particulate matter (SPM) samples from German rivers at different locations in time series from 2005 to 2020 were analyzed to investigate temporal and spatially resolved trends. In this study 3 PFAS mass balances approaches were utilized: (i) PFAA target vs. PFAS dTOPA, (ii) PFAS target vs. EOF and (iii) PFAS target vs. PFAS dTOPA vs. organofluorines NTS vs. EOF. Mass balance approach (i) revealed high proportions of precursor substances in SPM samples. For the time resolved analysis an increase from 94% (2005) to 97% in 2019 was observable. Also for the spatial resolved analysis precursor proportions were high with >84% at all sampling sites. Mass balance approach (ii) showed that the unidentified EOF (uEOF) fraction increased over time from 82% (2005) to 99% (2019). Furthermore, along the river courses the uEOF increased. In the combined mass balance approach (iii) using 4 different analytical approaches EOF fractions were further unraveled. The EOF pattern was fully explainable at the sampling sites at Saar and Elbe rivers. For the time resolved analysis, an increased proportion of the EOF was now explainable. However, still 27% of the EOF for the time resolved analysis and 25% of the EOF for the spatial resolved analysis remained unknown. Therefore, in a complementary approach, both the EOF and dTOPA reveal unknown gaps in the PFAS mass balance and are valuable contributions to PFAS risk assessment. Further research is needed to identify organofluorines summarized in the EOF parameter.

PFAS-Contaminated Soil Site in Germany: Nontarget Screening before and after Direct TOP Assay by Kendrick Mass Defect and FindPFΔS

Soil contaminations with per- and polyfluoroalkyl substances (PFAS) are of great concern due to their persistence, leading to continuous, long-term groundwater contamination. A composite sample from contaminated agricultural soil from northwestern Germany (Brilon-Scharfenberg, North Rhine-Westphalia) was investigated in depth with nontarget screening (NTS) (Kendrick mass defect and MS² fragment mass differences with FindPFΔS). Several years ago, selected PFCAs and PFSAs were identified on this site by detection in nearby surface and drinking water. We identified 10 further PFAS classes and 7 C₈-based PFAS (73 single PFAS) previously unknown in this soil including some novel PFAS. All PFAS classes except for one class comprised sulfonic acid groups and were semi-quantified with PFSA standards from which ∼97% were perfluorinated and are not expected to be degradable. New identifications made up >75% of the prior known PFAS concentration, which was estimated to >30 μg/g. Pentafluorosulfanyl (-SF₅) PFSAs are the dominant class (∼40%). Finally, the soil was oxidized with the direct TOP (dTOP) assay, revealing PFAA precursors that were covered to a large extent by identified H-containing PFAS and additional TPs (perfluoroalkyl diacids) were detected after dTOP. In this soil, however, dTOP + target analysis covers <23% of the occurring PFAS, highlighting the importance of NTS to characterize PFAS contaminations more comprehensively.

Target and nontarget screening of PFAS in drinking water for a large-scale survey of urban and rural communities in Québec, Canada

Limited monitoring data are available regarding the occurrence of emerging per- and polyfluoroalkyl substances (PFAS) in drinking water. Here, we validated an analytical procedure for 42 PFAS with individual detection limits of 0.001-0.082 ng/L. We also evaluated how different sample pH conditions, dechlorinating agents, and storage holding times might affect method performance. PFAS were analyzed in tap water samples collected at a large spatial scale in Quebec, Canada, covering 376 municipalities within 17 administrative regions. Target and nontarget screening revealed the presence of 31 and 23 compounds, respectively, representing 24 homolog classes. Overall, 99.3% of the tap water samples were positive for at least one PFAS, and the ƩPFAS ranged from below detection limits to 108 ng/L (95th percentile: 13 ng/L). On average, ƩPFAS was 12 times higher in tap water produced from surface water than groundwater; however, 6 of the top 10 contaminated locations were groundwater-based. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) had high detection rates (88% and 80%, respectively). PFOS (median: 0.15 ng/L; max: 13 ng/L) and PFOA (median: 0.27 ng/L; max: 8.1 ng/L) remained much lower than current Health Canada guidelines but higher than USEPA's interim updated health advisories. Short-chain (C3-C6) perfluoroalkyl sulfonamides were also recurrent, especially the C4 homolog (FBSA: detection rate of 50%). The 6:2 fluorotelomer sulfonyl propanoamido dimethyl ethyl sulfonate (6:2 FTSO2PrAd-DiMeEtS) was locally detected at ∼15 ng/L and recurred in 8% of our samples. Multiple PFAS that are most likely to originate from aqueous film-forming foams were also reported for the first time in tap water, including X:3 and X:1:2 fluorotelomer betaines, hydroxylated X:2 fluorotelomer sulfonates, N-trimethylammoniopropyl perfluoroalkane sulfonamides (TAmPr-FHxSA and TAmPr-FOSA), and N-sulfopropyl dimethylammoniopropyl perfluoroalkane sulfonamidopropyl sulfonates (N-SPAmP-FPeSAPS and N-SPAmP-FHxSAPS).

Total Oxidizable Precursor (TOP) Assay-Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

The comprehensive characterization of per- and polyfluoroalkyl substances (PFASs) is necessary for the effective assessment and management of risk at contaminated sites. While current analytical methods are capable of quantitatively measuring a number of specific PFASs, they do not provide a complete picture of the thousands of PFASs that are utilized in commercial products and potentially released into the environment. These unmeasured PFASs include many PFAS precursors, which may be converted into related PFAS chemicals through oxidation. The total oxidizable precursor (TOP) assay offers a means of bridging this gap by oxidizing unknown PFAS precursors and intermediates and converting them into stable PFASs with established analytical standards. The application of the TOP assay to samples from PFAS-contaminated sites has generated several new insights, but it has also presented various technical challenges for laboratories. Despite the increased number of literature studies that include the TOP assay, there is a critical and growing gap in the application of this method beyond researchers in academia. This article outlines the benefits and challenges of using the TOP assay with aqueous samples for site assessments and suggests ways to address some of its limitations.

Occurrence, Fate, and Related Health Risks of PFAS in Raw and Produced Drinking Water

This study investigates human exposure to per- and polyfluoroalkyl substances (PFAS) via drinking water and evaluates human health risks. An analytical method for 56 target PFAS, including ultrashort-chain (C2-C3) and branched isomers, was developed. The limit of detection (LOD) ranged from 0.009 to 0.1 ng/L, except for trifluoroacetic-acid and perfluoropropanoic-acid with higher LODs of 35 and 0.24 ng/L, respectively. The method was applied to raw and produced drinking water from 18 Dutch locations, including groundwater or surface water as source, and applied various treatment processes. Ultrashort-chain (300 to 1100 ng/L) followed by the group of perfluoroalkyl-carboxylic-acids (PFCA, ≥C4) (0.4 to 95.1 ng/L) were dominant. PFCA and perfluoroalkyl-sulfonic-acid (≥C4), including precursors, showed significantly higher levels in drinking water produced from surface water. However, no significant difference was found for ultrashort PFAS, indicating the need for groundwater protection. Negative removal of PFAS occasionally observed for advanced treatment indicates desorption and/or degradation of precursors. The proportion of branched isomers was higher in raw and produced drinking water as compared to industrial production. Drinking water produced from surface water, except for a few locations, exceed non-binding provisional guideline values proposed; however, all produced drinking waters met the recent soon-to-be binding drinking-water-directive requirements.

A new on-line SPE LC-HRMS method for simultaneous analysis of selected emerging contaminants in surface waters

In recent years emerging contaminants (ECs) have received significant attention due to their widespread detection in surface waters and concerns that these compounds can cause adverse ecological and/or human health effects. Therefore, accurate methods for determining and quantifying ECs in surface water are essential for estimating their environmental impact. This work describes the development, validation and application of a sensitive multiclass method for simultaneous determination of 22 per and polyfluorinated alkyl substances (PFASs), 3 pharmaceuticals, 15 pesticides, and 2 bisphenols in surface water using on-line solid phase extraction (SPE) coupled with ultra-performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS). The method allows simultaneous sample clean-up from interfering matrices and lower limits of detection (LODs) by injecting a large sample volume into the LC system without compromising chromatographic efficiency and resolution. Linearity of response over several orders of magnitude was demonstrated for all tested compounds (R2 > 0.99), with the LODs ranging from 0.8 and 33.7 pg mL-1, allowing detection of ECs at trace levels in surface water. The method showed acceptable accuracy and precision (CV, % and RE below 20%) for all tested ECs. It also provided recoveries between 60% and 130% for all tested ECs. The validated method was successfully applied for analysis of surface water samples from three rivers (Cam, Ouse and Thames) in England. Several ECs, including perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), perfluorohexane sulfonic acid (PFHxS), dimethyl-metatoluamide (DEET) and ibuprofen were observed in analysed surface water above the method's limit of quantitation (LOQ), with concentrations ranging between 3.5 and 460 pg mL-1.

Trace Analysis Method Based on UPLC-MS/MS for the Determination of (C2-C18) Per-and Polyfluoroalkyl Substances and Its Application to Tap Water and Bottled Water

As the usage of long-chain perfluoroalkyl and polyfluoroalkyl substances (PFASs) may be gradually restricted, short-chain and even ultra-short-chain PFASs have been widely produced and used, which has put forward new requirements for the simultaneous analysis of the above substances. Using solid phase extraction two-fraction elution and ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS), an experimental method was established for the simultaneous analysis of ultrashort-chain, short-chain, and long-chain PFASs and the precursor perfluorohexanesulfonamide (FHxSA) in low-concentration water, such as tap water and bottled water. By optimizing the volume of methanol in the first-fraction elution, the concentration of ammonia in the second-fraction elution, and the concentration of ammonium acetate in the mobile phase, the high recovery and low detection limit (0.01-3 ng/L) were obtained. In addition, this method was used to measure nine tap water samples and six bottled water samples for validation, and the results showed that the concentration of PFASs in bottled water was lower than that in tap water. This study first reported the trifluoroacetic acid concentration in bottled water (6.61 ± 9.60 ng/L), which was lower than that in tap water (1712 ± 174 ng/L). The main substances in tap water and bottled water are both ultrashort-chain PFASs (C2-C3), accounting for more than 50%. There are few reports on the simultaneous analysis of ultrashort-chain, short-chain, and long-chain PFASs (C2-C18) and the precursor FHxSA in low-concentration water samples, and the new method can be further developed for different environmental media.

Targeted Per- and Polyfluoroalkyl substances (PFAS) assessments for high throughput screening: Analytical and testing considerations to inform a PFAS stock quality evaluation framework

Per- and polyfluoroalkyl substances (PFAS) represent a large chemical class lacking hazard, toxicokinetic, and exposure information. To accelerate PFAS hazard evaluation, new approach methodologies (NAMs) comprised of in vitro high-throughput toxicity screening, toxicokinetic data, and computational modeling are being employed in read across strategies to evaluate the larger PFAS landscape. A critical consideration to ensure robust evaluations is a parallel assessment of the quality of the screening stock solutions, where dimethyl sulfoxide (DMSO) is often the diluent of choice. Challenged by the lack of commercially available reference standards for many of the selected PFAS and reliance on mass spectrometry approaches for such an evaluation, we developed a high-throughput framework to evaluate the quality of screening stocks for 205 PFAS selected for these NAM efforts. Using mass spectrometry coupled with either liquid or gas chromatography, a quality scoring system was developed that incorporated observations during mass spectral examination to provide a simple pass or fail notation. Informational flags were used to further describe findings regarding parent analyte presence through accurate mass identification, evidence of contaminants and/or degradation, or further describe characteristics such as isomer presence. Across the PFAS-DMSO stocks tested, 148 unique PFAS received passing quality scores to allow for further in vitro testing whereas 57 received a failing score primarily due to detection issues or confounding effects of DMSO. Principle component analysis indicated vapor pressure and Henry's Law Constant as top indicators for a failed quality score for those analyzed by gas chromatography. Three PFAS in the hexafluoropropylene oxide family failed due to degradation in DMSO. As the PFAS evaluated spanned over 20 different structural categories, additional commentary describes analytical observations across specific groups related to PFAS stock composition, detection, stability, and methodologic considerations that will be useful for informing future analytical assessment and downstream HTS efforts. The high-throughput stock quality scoring workflow presented holds value as a tool to evaluate chemical presence and quality efficiently and for informing data inclusion in PFAS or other NAM screening efforts.

Comprehensive investigation of persistent and mobile chemicals and per- and polyfluoroalkyl substances in urine of flemish adolescents using a suspect screening approach

Persistent and mobile chemicals (PMs) and per- and polyfluoroalkyl substances (PFAS) are groups of chemicals that have received recent global attention due to their potential health effects on the environment and humans. In this study, exposure to a broad range of PMs and PFAS was investigated in Flemish adolescents' urine samples (n = 83) using a suspect screening approach. For this purpose, three sample preparation methods were evaluated, and a basic liquid-liquid extraction was optimized for urine analysis based on the extraction efficiency of PMs (53-80%) and PFAS (>70%). In total, 9 PMs were identified in urine samples at confidence levels (CL) 1-3 and, among them, acetaminophen, 4-aminophenol, 2,2,6,6-tetramethyl-4-piperidone, trifluoroacetic acid (TFAA), sulisobenzone, ethyl sulfate, and 1,2-benzisothiazol-3(2H)-one 1,1-dioxide were confirmed at CL 1 and 2. In addition, the detection and identification of 2,2,6,6-tetramethyl-4-piperidone, 4-aminophenol, TFAA, and m-(2,3-epoxypropoxy)-N,N-bis(2,3-epoxypropyl) aniline (CL 3), has been reported for the first time in human urine in this study. For PFAS, only 2 compounds were identified at CL 4, implying that urine is not a suitable matrix for suspect screening of such compounds. A significant difference between sexes was observed in the detection rate of identified PMs, in particular for acetaminophen, 4-aminophenol, and sulisobenzone. The findings of this study can be used in future human biomonitoring programs, such as by including the newly identified compounds in quantitative methods or monitoring in other human matrices (e.g., serum).

Detection methods for sub-nanogram level of emerging pollutants - Per and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are organofluorine compounds has been manufactured for more than five decades and used in different purposes. Among persistent organic pollutants, PFAS are toxic, bioaccumulative in humans, wildlife, and global environment. As per environmental protection agency (EPA) guidelines, the perfluorooctanoate and perfluorooctane sulfonate permissible limit was 0.07 ng/L in drinking water. When the concentration exceeds the acceptable limit, it has negative consequences for humans. In such a case, PFAS monitoring is critical, and a quick detection technique are highly needed. Health departments and regulatory agencies have interests in monitoring of PFAS presences and exposures. For the detection of PFAS, numerous highly precise and sensitive chromatographic methods are available. However, the drawbacks of analytical techniques include timely sample preparations and the lack of on-site applicability. As a result, there is an increasing demand for simple sensor systems for monitoring of PFAS in real field samples. In this review, we first describe the sample pre-treatment and analytical techniques for the detection of PFAS. Second, we broadly discussed available sensor system for the quantification of PFAS in different filed samples. Finally, future trends in PFASs sensor are also presented.

The occurrence of perfluoroalkyl substances (PFAS) in drinking water in the Czech Republic: a pilot study

Drinking water is one of the main contributors to overall human exposure to per- and polyfluoroalkyl substances (PFAS), a broad group of environmental contaminants with arising concerns on the impact on human health; therefore, it is necessary to monitor its quality. Here, we present a solid-phase extraction-based method to determine 22 PFAS in water, using 100 mL of the sample. The instrumental analysis employing an ultra-high-performance liquid chromatography coupled with tandem mass spectrometry achieved low limits of quantification (0.025-0.25 ng/L). The validated method (recoveries 70-120% and repeatabilities ≤ 20% at tested concentrations (0.05, 0.1 and 0.5 ng/L)) was applied to 67 tap water and 31 bottled water samples collected in the Czech Republic. The most abundant compounds were perfluorononanoic acid (88% positives; 0.034-13.3 ng/L) and perfluoroheptanoic acid (23% positives; 0.035-0.106 ng/L), respectively. ∑PFAS in positive samples ranged from 0.029 to 300 ng/L (99% positives, median 2.34 ng/L) in tap water data and 0.033 to 4.48 ng/L (32% positives, median 0.097 ng/L) in bottled water samples. Current-use fluoroalkyl ethers, dodecafluoro-3H-4,8-dioxanonanoate and 11-chloroeicosafluoro-3-oxaundecane-1-sulfonate, were occasionally detected in tap. Based on the median data, PFAS intake by an adult from a tap or bottled water represented units of % of the tolerable weekly intake set by the European Food Safety Authority and therefore did not represent a severe risk. The described method and obtained first data on PFAS in the Czech drinking water provided a solid basis for an ongoing national study on the presence of PFAS in tap water.

A pilot study on extractable organofluorine and per- and polyfluoroalkyl substances (PFAS) in water from drinking water treatment plants around Taihu Lake, China: what is missed by target PFAS analysis?

Per- and polyfluoroalkyl substances (PFAS) have raised concerns due to their worldwide occurrence and adverse effects on both the environment and humans as well as posing challenges for monitoring. Further collection of information is required for a better understanding of their occurrence and the unknown fractions of the extractable organofluorine (EOF) not explained by commonly monitored target PFAS. In this study, eight pairs of raw and treated water were collected from drinking water treatment plants (DWTPs) around Taihu Lake in China and analyzed for EOF and 34 target PFAS. Mass balance analysis of organofluorine revealed that at least 68% of EOF could not be explained by target PFAS. Relatively higher total target concentrations were observed in 4 DWTPs (D1 to D4) when compared to other samples with the highest sum concentration up to 189 ng L^-1. PFOA, PFOS and PFHxS were the abundant compounds. Suspect screening analysis identified 10 emerging PFAS (e.g., H-PFAAs, H-PFESAs and OBS) in addition to target PFAS in raw or treated water. The ratios PFBA/PFOA and PFBS/PFOS between previous and current studies showed significant replacements of short-chain to long-chain PFAS. The ratios of the measured PFAS concentrations to the guideline values showed that some of the treated drinking water exceeds guideline values, appealing for efforts on drinking water safety guarantee.

Increases in Trifluoroacetate Concentrations in Surface Waters over Two Decades

Trifluoroacetate (TFA) is a persistent perfluorinated alkanoic acid anion that has many anthropogenic sources, with fluorocarbon refrigerants being a major one. After an initial burst of research in the late 1990s and early 2000s, research on this ubiquitous pollutant declined as atmospheric emissions of the precursor compounds grew rapidly. Thus, there is little contemporaneous information about the concentrations of TFA in the environment and how they have changed over time. This research determined the change in TFA concentrations in streams by resampling a transect that was originally sampled in 1998. The transect was designed to determine the regional distribution of TFA both upwind and downwind of major metropolitan areas in Northern California as well as a set of globally remote sites in Alaska. The results showed that TFA concentrations increased by an average of 6-fold over the intervening 23 years, which resulted in a median concentration of 180 ng/L (range 21.3-2790). The highest concentrations were found in streams immediately downwind of the San Francisco Bay Area, while substantially lower concentrations were found in the upwind, regionally remote, and globally remote sites. The C3 to C5 perfluorinated alkanoic acids were also investigated, but they were rarely detected with this methodology.

Ultra-Short-Chain PFASs in the Sources of German Drinking Water: Prevalent, Overlooked, Difficult to Remove, and Unregulated

Per- and polyfluoroalkyl substances (PFASs) have been a focal point of environmental chemistry and chemical regulation in recent years, culminating in a shift from individual PFAS regulation toward a PFAS group regulatory approach in Europe. PFASs are a highly diverse group of substances, and knowledge about this group is still scarce beyond the well-studied, legacy long-chain, and short-chain perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs). Herein, quantitative and semiquantitative data for 43 legacy short-chain and ultra-short-chain PFASs (≤2 perfluorocarbon atoms for PFCAs, ≤3 for PFSAs and other PFASs) in 46 water samples collected from 13 different sources of German drinking water are presented. The PFASs considered include novel compounds like hexafluoroisopropanol, bis(trifluoromethylsulfonyl)imide, and tris(pentafluoroethyl)trifluorophosphate. The ultra-short-chain PFASs trifluoroacetate, perfluoropropanoate, and trifluoromethanesulfonate were ubiquitous and present at the highest concentrations (98% of sum target PFAS concentrations). "PFAS total" parameters like the adsorbable organic fluorine (AOF) and total oxidizable precursor (TOP) assay were found to provide only an incomplete picture of PFAS contamination in these water samples by not capturing these highly prevalent ultra-short-chain PFASs. These ultra-short-chain PFASs represent a major challenge for drinking water production and show that regulation in the form of preventive measures is required to manage them.

Method for extraction and analysis of per- and poly-fluoroalkyl substances in contaminated asphalt

The legacy use of aqueous film-forming foam (AFFF) has led to the generation of large volumes of per- and poly-fluoroalkyl substances (PFAS)-contaminated asphalt materials, especially at airports and fire training areas. The management of such PFAS-contaminated asphalt materials requires an understanding of PFAS concentrations in these materials. This study, therefore, aimed to develop a suitable extraction methodology for the analysis of 22 target PFAS (i.e., carboxylic acids, sulfonic acids and fluorotelomers) in asphalt materials. A series of experiments was conducted to optimise extraction solvent composition, as well as to assess the performance of the chosen method under various conditions (i.e., sonication temperature, PFAS contamination level, asphalt core composition and timing of stable isotope addition used as internal standard). The methanol-based extractants performed best due to their accuracy and precision, which were within the acceptable range (extraction efficiency between 70 and 130% and RSD < 20%). The method which involved three successive extractions with methanol/1% NH₃ by ultrasonication at 25 °C was selected due to its performance and ease of operation. The mean recovery of a vast majority of PFAS was found to be in the acceptable range. Tests on the timing of addition of stable isotope (SI)-labelled PFAS internal standards indicate that the recoveries obtained, regardless of when the stable isotopes were added, were within the acceptable range for PFAS. The accuracy and precision of PFAS recoveries were not affected by PFAS spike level (2 μg kg^-1 and 200 μg kg^-1), as well as sample composition (based on the location of asphalt material in the field). Low RSDs were achieved for asphalt cores collected from a contaminated site covering a wide range of concentrations (from LOQ to 2135 mg kg^-1), demonstrating the suitability of the sample preparation method for real-world samples. The results from the interlaboratory testing were also in good agreement and validated the proposed PFAS extraction and analytical approach.

A fast and simple PFAS extraction method utilizing HR-CS-GFMAS for soil samples

Here, we describe an optimized fast and simple extraction method for the determination of per- and polyfluorinated alkyl substances (PFASs) in soils utilizing high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). To omit the bias of the solid phase extraction (SPE) step commonly used during the analysis of extractable organically bound fluorine (EOF) we optimized a fast and simple SPE-free extraction method. The developed extraction method consists of a liquid-solid extraction using acidified methanol without any additional SPE. Four extraction steps were representative to determine a high proportion of the EOF (>80% of eight extractions). Comparison of the optimized method with and without an additional SPE clean-up step revealed a drastic underestimation of EOF concentrations using SPE. Differences of up to 94% were observed which were not explainable by coextracted inorganic fluoride. Therefore, not only a more accurate but also a more economic as well as ecologic method (bypassing of unnecessary SPE) was developed. The procedural limit of quantification (LOQ) of the developed method was 10.30 μg/kg which was sufficient for quantifying EOF concentrations in all tested samples. For future PFAS monitoring and potential regulative decisions the herein presented optimized extraction method can offer a valuable contribution.

Iron-Doped Bimodal Mesoporous Silica Nanomaterials as Sorbents for Solid-Phase Extraction of Perfluoroalkyl Substances in Environmental Water Samples

In this work, sorbets based on UVM-7 mesoporous silica doped with Fe were synthesized and applied to solid-phase extraction of perfluoroalkyl substances from environmental water samples. These emerging pollutants were then determined by liquid chromatography coupled with a mass spectrometry detector. Thus, Fe-UVM-7 mesoporous silica materials with different contents of iron, as well as different pore sizes (by using alkyltrimethilamonium bromide surfactants with different organic tail lengths) were synthesized, and their structure was confirmed for the first time by transmission electron microscopy, nitrogen adsorption–desorption, X-ray diffraction, and Raman spectroscopy. After comparison, Fe50-UVM-7-C₁₂ was selected as the best material for analyte retention, and several extraction parameters were optimized regarding the loading and elution step. Once the method was developed and applied to real matrices, extraction efficiencies in the range of 61–110% were obtained for analytes with C₈–C₁₄ chain length, both perfluoroalkyl carboxylates, and perfluoroalkyl sulfonates. Likewise, limits of detection in the range of 3.0–8.1 ng L⁻¹ were obtained for all target analytes. In the analysis of real well-water samples, no target compounds were detected. Spiked samples were analyzed in comparison to Oasis WAX cartridges, and statistically comparable results were achieved.

Occurrence and fate of poly- and perfluoroalkyl substances (PFAS) in urban waters of New Zealand

Information on the occurrence of PFAS in aquatic matrices of countries with no PFAS manufacturing, e.g., New Zealand, is limited. Also, the fingerprint of PFAS along an urban water cycle, following water path from wastewater treatment plant (WWTP) effluent to treated drinking water has not been widely assessed. Hence, 38 long-, short-, ultrashort-chain PFAS and fluorinated alternatives (including precursors) were monitored in this study by collecting composite samples from two urban WWTPs of New Zealand and grab samples from the water bodies receiving the WWTPs' effluents and a drinking water treatment plant, whose source water received the effluent of one of the studied WWTPs. ∑PFAS at concentrations 0.1 - 13 ng/L were detected in all wastewater samples, including influents and different treatment stages of the two WWTPs (WW1 and WW2). The fate of most PFAS was similar in the two WWTPs, despite large differences in WWTPs' PFAS loads in the influents, serving populations (1.6 vs 0.16 million), total capacities (300 vs 54 million liters per day), and designs (aerobic and anoxic secondary treatment vs aerobic only). The fate of PFAS in WWTPs appeared to be driven by a range of processes. For instance, a simultaneous increase (41.6%) in short-chain perfluorohexanoic acid (PFHxA) concentrations and decrease (49.7%) in precursor 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations after secondary biological treatment suggested possible transformation of 6:2 FTS into PFHxA during the treatment. In contrast, the reason behind an average decrease of 35% in ultrashort-chain perfluoropropionic acid (PFPrA) concentrations after treatment was unclear, and further studies are recommended. The concentrations of a linear isomer of long-chain perfluorosulfonic acid (PFOS-L) decreased (48%) in the effluent, possibly due to its partitioning to sludge. Although the concentrations of PFAS in coastal waters suggested that the WW1 effluent is a potential source of PFAS, earlier dispersion model and no detection of PFAS in the receiving waters of WW2 implied that other sources, such as septic systems, peripheral industries, and the airport, could also be contributing to PFAS in coastal waters. The source of ultrashort-chain PFPrA (5.5 ng/L) detected in the treated drinking water produced from that river was unclear. The monitoring results confirm incomplete removal of PFAS in WWTPs, indicate a possible transformation of unknown precursors present in wastewater into short-chain perfluoroalkylcarboxylic acids (PFCAs) during biological treatment, and reveal a possible accumulation of perfluoroalkylsulfonic acids (PFSAs) in the sludge, overall suggesting the circulation of PFAS in urban water systems.

Analysis of hydrophilic per- and polyfluorinated sulfonates including trifluoromethanesulfonate using solid phase extraction and mixed-mode liquid chromatography-tandem mass spectrometry

Ultra-hydrophilic per- and polyfluorinated sulfonates (PFSA) are increasingly scrutinized in recent years due to their ubiquitous occurrence, persistence, and aqueous mobility in the environment, yet analysis remains a challenge. This study developed methods for the analysis of trifluoromethanesulfonate, perfluorobutanesulfonate, 10-camphorsulfonate, and a di-fluorinated sulfonate utilizing mixed-mode liquid chromatography, where all analytes were adequately retained and separated. Chromatography and electrospray ionization parameters were optimized; instrumental limits of quantification for the anionic target analytes were in the range of 4.3 - 16.1 ng L^-1. Solid phase extraction (SPE) methods were developed using Oasis WAX cartridges; SPE recoveries for the analytes ranged from 86% to 125%. Salinity and total organic carbon both impaired the SPE performance to different extents, depending on the respective analyte. Utilizing widely accessible instrumentation and materials, this is a single method to simultaneously analyze conceivably the most hydrophilic PFAS chemical, i.e., trifluoromethanesulfonate, and moderately hydrophobic PFSAs.

Mass Balance of Perfluoroalkyl Acids, Including Trifluoroacetic Acid, in a Freshwater Lake

Perfluoroalkyl acids (PFAAs) are highly persistent chemicals that are ubiquitously found in the environment. The atmospheric degradation of precursor compounds has been identified as a source of PFAAs and might be an important pathway for contamination. Lake Vättern is one of Sweden's largest lakes and is an important source for drinking water. In addition to contamination via atmospheric deposition, the lake is subject to several potential contamination sources via surface water inflow. The relevance of different sources is not well understood. A mass balance of selected PFAAs was assembled based on measured concentrations in atmospheric deposition, surface water from streams that constitute the main inflow and outflow, and surface water in the lake. The largest input was seen for trifluoroacetic acid (150 kg/year), perfluoropropanoic acid (1.6 kg/year), perfluorobutanoic acid (4.0 kg/year), and perfluoro-octanoic acid (1.5 kg/year). Both atmospheric deposition and surface water inflow was found to be important input pathways. There was a positive correlation between the input of most perfluoroalkyl carboxylic acids via atmospheric deposition and global radiation and between the input via surface water inflow and catchment area. These findings highlight the importance of atmospheric oxidation of volatile precursor compounds for contamination in surface waters.

Development and validation of an LC-MS/MS method for the quantitation of 30 legacy and emerging per- and polyfluoroalkyl substances (PFASs) in human plasma, including HFPO-DA, DONA, and cC6O4

Per- and polyfluoroalkyl substances (PFASs) include persistent organic pollutants whose spread is still ubiquitous. Efforts to substitute substances of high concern with fluorinated alternatives, such as HFPO-DA (GenX), DONA (ADONA), and cC6O4, have been made. The aim of this work was to develop and validate an isotopic dilution liquid chromatography-tandem mass spectrometry (LC–MS/MS) method suitable to quantify 30 PFASs in human plasma. Analytes included legacy PFASs (PFOA, PFOS, and PFHxS), fluorinated alternatives (PFBA, PFBS, 6:2 FTSA, HFPO-DA, DONA, and cC6O4), and newly identified compounds (F-53B and PFECHS). The sample preparation was rapid and consisted of simple protein precipitation and centrifugation. Calibration standards and quality control solutions were prepared with a human pooled plasma containing relatively low background levels of the considered analytes. A complete validation was carried out: the lower limits of quantitation (LLOQs) ranged from 0.009 to 0.245 µg/L; suitable linearity (determination coefficients, R² 0.989–0.999), precision (2.0–19.5%, relative standard deviation), and accuracy (87.9–113.1% of theoretical) were obtained for considered concentration ranges. No significant variations of analyte responses were recorded under investigated storage conditions and during matrix effect tests. The external verification confirmed the accuracy of the method, although limited to 12 analytes. The method was also applied to 38 human plasma samples to confirm its applicability. The developed assay is suitable for large-scale analyses of a wide range of legacy and emerging PFASs in human plasma. To our knowledge, this is the first published method including cC6O4 for human biomonitoring.

Light-Induced Advanced Oxidation Processes as PFAS Remediation Methods: A Review

PFAS substances, which have been under investigation in recent years, are certainly some of the most critical emerging contaminants. Their presence in drinking water, correlated with diseases, is consistently being confirmed by scientific studies in the academic and health sectors. With the aim of developing new technologies to mitigate the water contamination problem, research activity based on advanced oxidation processes for PFAS dealkylation and subsequent mineralization is active. While UV radiation could be directly employed for decontamination, there are nevertheless considerable problems regarding its use, even from a large-scale perspective. In contrast, the use of cheap, robust, and green photocatalytic materials active under near UV-visible radiation shows interesting prospects. In this paper we take stock of the health problems related to PFAS, and then provide an update on strategies based on the use of photocatalysts and the latest findings regarding reaction mechanisms. Finally, we detail some brief considerations in relation to the economic aspects of possible solutions.

Sensors for detecting per- and polyfluoroalkyl substances (PFAS): A critical review of development challenges, current sensors, and commercialization obstacles

Per- and polyfluoroalkyl substances (PFAS) are a class of compounds that have become environmental contaminants of emerging concern. They are highly persistent, toxic, bioaccumulative, and ubiquitous which makes them important to detect to ensure environmental and human health. Multiple instrument-based methods exist for sensitive and selective detection of PFAS in a variety of matrices, but these methods suffer from expensive costs and the need for a laboratory and highly trained personnel. There is a big need for fast, inexpensive, robust, and portable methods to detect PFAS in the field. This would allow environmental laboratories and other agencies to perform more frequent testing to comply with regulations. In addition, the general public would benefit from a fast method to evaluate the drinking water in their homes for PFAS contamination. A PFAS sensor would provide almost real-time data on PFAS concentrations that can also provide actionable information for water quality managers and consumers around the planet. In this review, we discuss the sensors that have been developed up to this point for PFAS detection by their molecular detection mechanism as well as the goals that should be considered during sensor development. Future research needs and commercialization challenges are also highlighted.

LC-HRMS screening of per- and polyfluorinated alkyl substances (PFAS) in impregnated paper samples and contaminated soils

High per- and polyfluorinated alkyl substance (PFAS) concentrations have been detected in agricultural soils in Southwest Germany. Discharges of PFAS-contaminated paper sludge and compost are suspected to be the cause of the contamination. Perfluorinated carboxylic acids (PFCAs) have been detected also in groundwater, drinking water, and plants in this area. Recently, previously unknown compounds have been identified by high-resolution mass spectrometry (HRMS). Major contaminants were polyfluorinated dialkylated phosphate esters (diPAPs) and N-ethyl perfluorooctane sulfonamide ethanol–based phosphate diester (diSAmPAP). In this study, HRMS screening for PFAS was applied to 14 soil samples from the contaminated area and 14 impregnated paper samples which were from a similar period than the contamination. The paper samples were characterized by diPAPs (from 4:2/6:2 to 12:2/12:2), fluorotelomer mercapto alkyl phosphates (FTMAPs; 6:2/6:2 to 10:2/10:2), and diSAmPAP. In soil samples, diPAPs and their transformation products (TPs) were the major contaminants, but also FTMAPs, diSAmPAP, and their TPs occurred. The distribution patterns of the carbon chain lengths of the precursor PFAS in soil samples were shown to resemble those in paper samples. This supports the hypothesis that paper sludge is a major source of contamination. The presence of major degradation products like PFCAs, FTSAs, or PFOS and their distribution of carbon chain lengths indicate the activity of biotic or abiotic degradation processes and selective leaching processes from the upper soil horizons.

Ion exchange solid phase microextraction coupled to liquid chromatography/laminar flow tandem mass spectrometry for the determination of perfluoroalkyl substances in water samples

Per- and polyfluoroalkyl substances (PFAS) are toxic and bioaccumulative compounds that are persistent in the environment due to their water and heat resistant properties. These compounds have been demonstrated to be ubiquitous in the environment, being found in water, soil, air and various biological matrices. The determination of PFAS at ultra-trace levels is thus critical to assess the extent of contamination in a particular matrix. In this work, solid phase microextraction (SPME) was evaluated as a pre-concentration technique to aid the quantitation of this class of pollutants below the EPA established advisory limits in drinking water at parts-per-trillion levels. Four model PFAS with varying physicochemical properties, namely hexafluoropropylene oxide dimer acid (GenX), perfluoro-1- butanesulfonate (PFBS), perfluoro-n-octanoic acid (PFOA) and perfluoro-1-octanesulfonate (PFOS) were studied as a proof of concept. Analysis was performed with the use of ultra-high pressure liquid chromatography-laminar flow tandem mass spectrometry (UHPLC-MS/MS). This study proposes the use of hydrophilic-lipophilic balance-weak anion-exchange/polyacrylonitrile (HLB-WAX/PAN) as a SPME coating, ideal for all model analytes. A sample volume of 1.5 mL was used for analysis, the optimized protocol including 20 min extraction, 20 min desorption and 6 min LC/MS analysis. This method achieved LOQs of 2.5 ng L^- 1 (PFOS) and 1 ng L ^- 1 (GenX, PFBS and PFOA) with satisfactory precision and accuracy values evaluated over a period of 5 days.

PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding

We synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly- and perfluoroalkyl substances (PFAS). Most human exposure assessments have focused on 2 to 5 legacy PFAS, and wildlife assessments are typically limited to targeted PFAS (up to ~30 substances). However, shifts in chemical production are occurring rapidly, and targeted methods for detecting PFAS have not kept pace with these changes. Total fluorine measurements complemented by suspect screening using high-resolution mass spectrometry are thus emerging as essential tools for PFAS exposure assessment. Such methods enable researchers to better understand contributions from precursor compounds that degrade into terminal perfluoroalkyl acids. Available data suggest that diet is the major human exposure pathway for some PFAS, but there is large variability across populations and PFAS compounds. Additional data on total fluorine in exposure media and the fraction of unidentified organofluorine are needed. Drinking water has been established as the major exposure source in contaminated communities. As water supplies are remediated, for the general population, exposures from dust, personal care products, indoor environments, and other sources may be more important. A major challenge for exposure assessments is the lack of statistically representative population surveys. For wildlife, bioaccumulation processes differ substantially between PFAS and neutral lipophilic organic compounds, prompting a reevaluation of traditional bioaccumulation metrics. There is evidence that both phospholipids and proteins are important for the tissue partitioning and accumulation of PFAS. New mechanistic models for PFAS bioaccumulation are being developed that will assist in wildlife risk evaluations. Environ Toxicol Chem 2021;40:631-657. © 2020 SETAC.

Ultrashort-chain perfluoroalkyl substance trifluoroacetate (TFA) in beer and tea - An unintended aqueous extraction

Trifluoroacetate (TFA) is an ultrashort-chain perfluoroalkyl substance, which is ubiquitously present in the aqueous environment. Due to its high mobility, it accumulates in plant material. The study presented here shows for the first time that TFA is a widely spread contaminant in beer and tea / herbal infusions. In 104beer samples from 23countries, TFA was detected up to 51 µg/L with a median concentration of 6.1 µg/L. An indicative brewing test and a correlation approach with potassium (K) indicate that the main source of TFA in beer is most likely the applied malt. It could be proven that the impact of the applied water is negligible in terms of TFA, which was supported by the analysis of numerous tap water samples from different countries. The unintended extraction of TFA was also demonstrated for tea / herbal infusions with a median concentration of 2.4 µg/L.

Determination of organically bound fluorine sum parameters in river water samples-comparison of combustion ion chromatography (CIC) and high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS)

In this study, we compare combustion ion chromatography (CIC) and high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) with respect to their applicability for determining organically bound fluorine sum parameters. Extractable (EOF) and adsorbable (AOF) organically bound fluorine as well as total fluorine (TF) were measured in samples from river Spree in Berlin, Germany, to reveal the advantages and disadvantages of the two techniques used as well as the two established fluorine sum parameters AOF and EOF. TF concentrations determined via HR-CS-GFMAS and CIC were comparable between 148 and 270 μg/L. On average, AOF concentrations were higher than EOF concentrations, with AOF making up 0.14–0.81% of TF (determined using CIC) and EOF 0.04–0.28% of TF (determined using HR-CS-GFMAS). The results obtained by the two independent methods were in good agreement. It turned out that HR-CS-GFMAS is a more sensitive and precise method for fluorine analysis compared to CIC. EOF and AOF are comparable tools in risk evaluation for the emerging pollutants per- and polyfluorinated alkyl substances; however, EOF is much faster to conduct.

Simultaneous determination of seven perfluoroalkyl carboxylic acids in water samples by 2,3,4,5,6-pentafluorobenzyl bromide derivatization and gas chromatography-mass spectrometry

A new derivatization reagent, 2,3,4,5,6-pentafluorobenzyl bromide (PFBBr), was employed to determine seven perfluoroalkyl carboxylic acids (PFCAs) simultaneously in tap water with gas chromatography-mass spectrometry (GC-MS) technique in this study. Firstly, seven PFCAs were derivatized to their corresponding esters under alkaline condition. The derivatization conditions including the amount of PFBBr and K₂CO₃, derivatization temperature and time were optimized to increase the derivatization efficiency. The 14 tap water samples collected from different places of China were enriched and purified through solid phase extraction pretreatment. The limits of detection (LODs) and the limits of quantitation (LOQs) ranged from 0.1 ng/L to 0.28 ng/L and from 0.3 ng/L to 0.84 ng/L, respectively. The new method offers a linear relationship in the range from 2 ng/L to 2000 ng/L, and the correlation coefficients ranged from 0.9938 to 0.9994. The results showed that GC-MS combined with pre-column derivatization is a reliable method for the analysis of PFCAs in the aqueous environment.

Prevalence of per- and polyfluoroalkyl substances (PFASs) in drinking and source water from two Asian countries

The present study focuses on the determination of the occurrence and levels of per- and polyfluoroalkyl substances (PFASs) in the drinking and source water from the Philippines and Thailand. A total of 46 samples (18 commercial bottled waters, 5 drinking water from vending machine (re-fill stations) and 23 source water) were analyzed using liquid chromatography with tandem high-resolution mass spectrometry. Using the targeted method, 12 different PFASs were detected in the drinking water samples with total quantifiable PFASs (∑PFASs) levels ranging from 7.16 to 59.49 ng/L; 15 PFASs were detected in source water with ∑PFASs ranging from 15.55 to 65.65 ng/L. A 100% detection frequency was observed for perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorosulfonic acid (PFOS) in all water samples. Six other PFASs, not included in the targeted analysis, were detected using the suspect screening approach. For the first time, the presence of 2-(N-methylperfluorooctanesulfonamido) acetic acid (N-MeFOSAA) in drinking water is reported, and 3 novel PFASs (C₅H₅OF_8, C₆H₄O₂F₆, and C₉H₂O₂F₁₆) were detected using suspect screening in source water. Combined results from target and suspect screening analysis showed that PFASs detected were predominantly (52%) short-chain (with fluorinated alkyl chain of ≤6) which could be explained by their high mobility in the environment. The detected PFASs levels in drinking water will not likely pose immediate health risk to consumers according to US EPA health advisory for PFOS and PFOA of 70 ng/L, but inclusion of bottled and drinking water from re-fill stations in monitoring programs is warranted.

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

Ultra-short-chain perfluoroalkyl acids have recently gained attention due to increasing environmental concentrations being observed. The most well-known ultra-short-chain perfluoroalkyl acid is trifluoroacetic acid (TFA) which has been studied since the 1990s. Potential sources and the fate of ultra-short-chain perfluoroalkyl acids other than TFA are not well studied and data reporting their environmental occurrence is scarce. The analytical determination of ultra-short-chain perfluoroalkyl acids is challenging due to their high polarity resulting in low retention using reversed-phase liquid chromatography. Furthermore, recent studies have reported varying extraction recoveries in water samples depending on the water matrix and different methods have been suggested to increase the extraction recovery. The present review gives an overview of the currently used analytical methods and summarizes the findings regarding potential analytical challenges. In addition, the current state of knowledge regarding TFA and other ultra-short-chain perfluoroalkyl acids, namely perfluoropropanoic acid, trifluoromethane sulfonic acid, perfluoroethane sulfonic acid, and perfluoropropane sulfonic acid‚ are reviewed. Both known and potential sources as well as environmental concentrations are summarized and discussed together with their fate and the environmental and human implications.

Applicability of mixed-mode chromatography for the simultaneous analysis of C1-C18 perfluoroalkylated substances

A new analytical method for the determination of 22 perfluoroalkylated (carboxylic and sulfonic) acids in water samples is presented. The method's objective was to achieve the simultaneous quantification of compounds with different chain lengths (from C₁ to C₁₈). To this end, 500 mL of water were extracted with Oasis WAX solid-phase extraction cartridges and eluted with 3 mL of 5% ammonia in methanol. After evaporation to dryness, extracts were reconstituted in methanol:ultrapure water (1:1) and analyzed by mixed-mode liquid chromatography-tandem mass spectrometry (MMLC-MS/MS) using a weak anion exchange/reversed-phase column. The method provided good results, with limits of quantification lower than 1 ng/L in river water for most of compounds, except the two perfluorocarboxylic acids with the longest alkyl chain (>C₁₄) and trifluoroacetic acid, for which a blank contamination problem was observed. The method proved good trueness and precision in both ultrapure and river water (R ≥ 81%, RSD ≤ 15%). After validation, the method was applied to the analysis of nine water samples where nine perfluoroalkylated acids were quantified. Seven of them were ultrashort- (C₁-C₄) and short-chain (C₄-C₈) perfluoroalkylated acids, pointing out the importance of developing methods capable to target such substances for further monitoring.

LC-MS screening of poly- and perfluoroalkyl substances in contaminated soil by Kendrick mass analysis

The application of contaminated paper sludge on arable land in southwest Germany caused the occurrence of a broad range of poly- and perfluoroalkyl substances (PFASs) on soil. Recently, the dead-end transformation products (TPs) perfluorooctanoic acid and perfluorooctanesulfonic acid were detected in groundwater and drinking water. The precursors and other transformation products mostly remained unknown. Therefore, HRMS screening by Kendrick mass analysis and assignment of homologous series in combination with suspect screening were applied to identify original PFASs and their TPs in four different soil samples from sites where contaminated paper sludge was applied. In total, twelve compound classes comprising more than 61 PFASs could be fully or tentatively identified. The data reveal that contamination mainly originates from polyfluorinated dialkylated phosphate esters (from 4:2/6:2 to 12:2/14:2), N-ethyl perfluorooctane sulfonamide ethanol–based phosphate diesters (only C₈/C₈) and transformation products of these precursors. Contamination patterns can be attributed to PFASs used for paper impregnation and can vary slightly from site to site.

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