HPLC–MS/MS methods for the determination of 52 perfluoroalkyl and polyfluoroalkyl substances in aqueous samples

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.

Rapid Determination of 12 Classes of Per- and Polyfluoroalkyl Substances in Water Samples from Environmental Forensic Cases

The widespread use of per- and polyfluoroalkyl substances (PFASs) with different physico-chemical properties poses a great threat to the environment and human health. Simultaneous detection of different classes of PFASs is a difficult task, especially for rapid analysis of polluted water samples in environmental forensic cases. In this study, a simple sample preparation ultrahigh-performance liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry was established for the detection of PFASs in a wide range of water matrices. By optimizing the conditions of pretreatment and the parameters of the instrument, the developed method provided good linearity of calibration standards (R2 > 0.99), and demonstrated excellent MLOQ (0.008-1.2 µg/L), with spiked recoveries ranging from 57.7% to 151% for 47 targets in surface water samples, and from 45.7 to 165% for 46 targets in ground and waste water samples, respectively. This method required an injection volume of 3 µL and an analysis time of only 18 min per sample. The validation method was successfully applied to the analysis of 20 environmental water samples, in which 15 target substances with different concentrations were detected, with total concentrations of 0.082 to 262.455 μg/L. The method is simple and exclusive, and can rapidly confirm the occurrence of PFASs in different water samples, providing a convenient and fast high-throughput analysis, which is especially suitable for the application in the environmental forensic investigation of PFASs pollution.

Emerging and legacy per- and polyfluoroalkyl substances (PFAS) in fluorochemical wastewater along full-scale treatment processes: Source, fate, and ecological risk

The increasing applications of emerging per- and polyfluoroalkyl substances (PFAS) have raised global concern. However, the release of emerging PFAS from the fluorochemical industry remains unclear. Herein, the occurrence of 48 emerging and legacy PFAS in wastewater from 10 fluorochemical manufacturers and mass flows of PFAS in a centralized wastewater treatment plant were investigated. Their distribution and ecological risk in neighboring riverine water were also evaluated. In wastewater from fluorochemical manufacturers, PFAS concentrations were in the range of 14,700-5200,000 ng/L and 2 H,2 H-perfluorooctanoic acid (6:2 FTCA), perfluorooctanoic acid (PFOA), N-ethyl perfluorooctane sulfonamide (N-EtFOSA), and 1 H,1 H,2 H,2 H-perfluorodecanesulfonate (8:2 FTS) were the major PFAS detected. Several PFAS displayed increased mass flows after wastewater treatment, especially PFOA and 6:2 FTCA. The mass flows of PFAS increased from - 20% to 233% after the activated sludge system but decreased by only 0-13% after the activated carbon filtration. In riverine water, PFAS concentrations were in the range of 5900-39,100 ng/L and 6:2 FTCA, 1 H,1 H,2 H,2 H-perfluorodecyl phosphate monoester (8:2 monoPAP), 1 H,1 H,2 H,2 H-perfluorooctyl phosphate monoester (6:2 monoPAP), PFOA, and perfluorohexanoic acid (PFHxA) were the major PFAS detected. PFOA and 6:2 FTCA exhibited comparable hazard quotients for ecological risk. Current wastewater treatment processes cannot fully remove various PFAS discharged by fluorochemical manufacturers, and further investigations on their risk are needed for better chemical management.

All-in-one strategy to construct bifunctional covalent triazine-based frameworks for simultaneous extraction of per- and polyfluoroalkyl substances and polychlorinated naphthalenes in foods

Per- and polyfluoroalkyl substances (PFASs) and polychlorinated naphthalenes (PCNs) are of growing concern due to their toxic effects on the environment and human health. There is an urgent need for strategies to monitor and analyze the coexistence of PFASs and PCNs, especially in food samples at trace levels, to ensure food safety. Herein, a novel β-cyclodextrin (β-CD) derived fluoro-functionalized covalent triazine-based frameworks named CD-F-CTF was firstly synthesized. This innovative framework effectively combines the porous nature of the covalent organic framework and the host-guest recognition property of β-CD enabling the simultaneous extraction of PFASs and PCNs. Under the optimal conditions, a simple and rapid method was developed to analyze PFASs and PCNs by solid-phase extraction (SPE) based simultaneous extraction and stepwise elution (SESE) strategy for the first time. When coupled with liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS), this method achieved impressive detection limits for PFASs (0.020 -0.023 ng/g) and PCNs (0.016 -0.075 ng/g). Furthermore, the excellent performance was validated in food samples with recoveries of 76.7-107 % (for PFASs) and 78.0-108 % (for PCNs). This work not only provides a simple and rapid technique for simultaneous monitoring of PFASs and PCNs in food and environmental samples, but also introduces a new idea for the designing novel adsorbents with multiple recognition sites.

Interspecies comparison of metabolism of two novel prototype PFAS

As a result of proposed global restrictions and regulations on current-use per-and polyfluoroalkyl substances (PFAS), research on possible alternatives is highly required. In this study, phase I in vitro metabolism of two novel prototype PFAS in human and rat was investigated. These prototype chemicals are intended to be safer-by-design and expected to mineralize completely, and thus be less persistent in the environment compared to the PFAS available on the market. Following incubation with rat liver S9 (RL-S9) fractions, two main metabolites per initial substance were produced, namely an alcohol and a short-chain carboxylic acid. While with human liver S9 (HL-S9) fractions, only the short-chain carboxylic acid was detected. Beyond these major metabolites, two and five additional metabolites were identified at very low levels by non-targeted screening for the ether- and thioether-linked prototype chemicals, respectively. Overall, complete mineralization during the in vitro hepatic metabolism of these novel PFAS by HL-S9 and RL-S9 fractions was not observed. The reaction kinetics of the surfactants was determined by using the metabolite formation, rather than the substrate depletion approach. With rat liver enzymes, the formation rates of primary metabolite alcohols were at least two orders of magnitude higher than those of secondary metabolite carboxylic acids. When incubating with human liver enzymes, the formation rates of single metabolite carboxylic acids, were similar or smaller than those experienced in rat. It also indicates that the overall metabolic rate and clearance of surfactants are significantly higher in rat liver than in human liver. The maximum formation rate of the thioether congener exceeded 10-fold that of the ether in humans but were similar in rats. Overall, the results suggest that metabolism of the prototype chemicals followed a similar trend to those reported in studies of fluorotelomer alcohols.

Using regular and transcriptomic analyses to investigate the biotransformation mechanism and phytotoxic effects of 6:2 fluorotelomer carboxylic acid (6:2 FTCA) in pumpkin (Cucurbita maxima L.)

Although 6:2 fluorotelomer carboxylic acid (6:2 FTCA), which is one of the most popular substitutes for perfluorooctanoic acid (PFOA), has been widely distributed in environments, little is known about its biotransformation mechanism and phytotoxic effects in plants. Here, we showed that 6:2 FTCA could be taken up by pumpkin (Cucurbita maxima L.) roots from exposure solution and acropetally translocated to shoots. Biotransformation of 6:2 FTCA to different carbon chain perfluorocarboxylic acid (PFCA) metabolites (C2-C7) via α-and β-oxidation in pumpkin was observed, and perfluorohexanoic acid (PFHxA) was the major transformation product. The results of enzyme assays, enzyme inhibition experiments and gene expression analysis indicated that cytochrome P450 (CYP450), glutathione-S-transferase (GST) and ATP-binding cassette (ABC) transporters were involved in the metabolism of 6:2 FTCA in pumpkin. Plant-associated rhizobacteria and endophyte also contributed to 6:2 FTCA degradation through β-oxidation. The chlorophyll (Chl) content and genes involved in photosynthesis were significantly improved by 6:2 FTCA. The reductions of antioxidant and metabolic enzyme activities reflected the antioxidant defense system and detoxification system of pumpkin were both damaged, which were further confirmed by the down-regulating associated genes encoding phenylpropanoid biosynthesis, endoplasmic reticulum-related proteins, ascorbate-glutathione cycle and ABC transporters. This study is helpful to understand the environmental behaviors and toxicological molecular mechanisms of 6:2 FTCA in plants.

Physicochemical properties and interactions of perfluoroalkyl substances (PFAS) - Challenges and opportunities in sensing and remediation

Per- and polyfluoroalkyl substances (PFAS) is a class of persistent organic pollutants that presents health and environmental risks. PFAS are ubiquitously present in the environment, but current remediation technologies are ineffective in degrading them into innocuous chemicals, especially high energy degradation processes often generate toxic short chain intermediates. Therefore, the best remediation strategy is to first detect the source of pollution, followed by capturing and mineralising or recycling of the compounds. The main objective of this article is to summarise the unique physicochemical properties and to critically review the intermolecular and intramolecular physicochemical interactions of PFAS, and how these interactions can become obstacles; and at the same time, how they can be applied to the PFAS sensing, capturing, and recycling process. The physicochemical interactions of PFAS chemicals are being reviewed in this paper includes, (1) fluorophilic interactions, (2) hydrophobic interactions, (3) electrostatic interactions and cation bridging, (4) ionic exchange and (5) hydrogen bond. Moreover, all the different influential factors to these interactions have also been reported. Finally, properties of these interactions are compared against one another, and the recommendations for future designs of affinity materials for PFAS have been given.

Insight into the mechanisms of neuroendocrine toxicity induced by 6:2FTCA via thyroid hormone disruption

6:2 fluorotonic carboxylic acid (6:2 FTCA), a novel substitute for perfluorooctanoic acid (PFOA), is being used gradually in industrial production such as coatings or processing aids, and its detection rate in the aqueous environment is increasing year by year, posing a potential safety risk to aquatic systems and public health. However, limited information is available on the effects and mechanism of 6:2 FTCA. Therefore, this study was conducted to understand better the neuroendocrine effects of early exposure to 6:2 FTCA and the underlying mechanisms on zebrafish. In this study, zebrafish embryos were treated to varied doses of 6:2 FTCA (0, 0.08 μg/mL, 0.8 μg/mL and 8 μg/mL) at 4 h post-fertilization (hpf) for a duration of six days, which exhibited a pronounced inhibition of early growth and induced a disorganized swim pattern characterized by reduced total swim distance and average swim speed. Simultaneously, the thyroid development of zebrafish larvae was partially hindered, accompanied by decreased T3 levels, altered genes associated with the expression of thyroid hormone synthesis, transformation and transportation and neurotransmitters associated with tryptophan and tyrosine metabolic pathways. Molecular docking results showed that 6:2 FTCA has a robust binding energy with the thyroid hormone receptor (TRβ). Moreover, exogenous T3 supplementation can partially restore the adverse outcomes. Our findings indicated that 6:2 FTCA acts as a thyroid endocrine disruptor and can induce neuroendocrine toxic effects. Furthermore, our results show that targeting TRβ may be a potentially therapeutic strategy for 6:2 FTCA-induced neuroendocrine disrupting effects.

Application of in-source fragmentation to the identification of perfluoropentanoic acid and perfluorobutanoic acid in environmental matrices and human serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is the most common analytical technique for per- and polyfluoroalkyl substances (PFASs) research and monitoring. The PFAS identification requires a minimum of two multiple reaction monitoring (MRM) transition ions as quantifier transition ion and qualifier transition ion, respectively. The second transition ion abundance for perfluoropentanoic acid (PFPeA) and perfluobutanoic acid (PFBA) is too low for practical use. A method using the in-source fragment ions as the precursor ion for MRM or pseudo-MRM has been developed and evaluated for PFPeA and PFBA identification in various environmental abiotic and biotic samples including water, soil, sediment, WWTP sludge, fruits, vegetables, egg, macrophytes, fish, dolphin liver and human serum. The PFPeA qualifier MRM transition ion (m/z = 219 > 69) has been successfully applied in all the matrices with spike recoveries (90-125%), signal to noise ratios (>10) and transition ions ratio variation (80-120%). The PFBA qualifier pseudo-MRM transition ion (m/z = 169 > 169) works well in all the matrices except dolphin liver sample. The interpretation of pseudo-MRM results should be with cautions due to lower specificity compared to MRM. In addition, this project indicated under typical chromatographic conditions the MRM isobaric interference does happen frequently to PFPeA quantifier transition ion (m/z = 263 > 219) in serum and fish composite samples, and to PFBA quantifier transition ion (m/z = 213 > 169) in macrophytes, fish composite and dolphin liver samples.

Target and Suspect Screening Integrated with Machine Learning to Discover Per- and Polyfluoroalkyl Substance Source Fingerprints

This study elucidates per- and polyfluoroalkyl substance (PFAS) fingerprints for specific PFAS source types. Ninety-two samples were collected from aqueous film-forming foam impacted groundwater (AFFF-GW), landfill leachate, biosolids leachate, municipal wastewater treatment plant effluent (WWTP), and wastewater effluent from the pulp and paper and power generation industries. High-resolution mass spectrometry operated with electrospray ionization in negative mode was used to quantify up to 50 target PFASs and screen and semi-quantify up to 2,266 suspect PFASs in each sample. Machine learning classifiers were used to identify PFASs that were diagnostic of each source type. Four C5-C7 perfluoroalkyl acids and one suspect PFAS (trihydrogen-substituted fluoroethernonanoic acid) were diagnostic of AFFF-GW. Two target PFASs (5:3 and 6:2 fluorotelomer carboxylic acids) and two suspect PFASs (4:2 fluorotelomer-thia-acetic acid and N-methylperfluoropropane sulfonamido acetic acid) were diagnostic of landfill leachate. Biosolids leachates were best classified along with landfill leachates and N-methyl and N-ethyl perfluorooctane sulfonamido acetic acid assisted in that classification. WWTP, pulp and paper, and power generation samples contained few target PFASs, but fipronil (a fluorinated insecticide) was diagnostic of WWTP samples. Our results provide PFAS fingerprints for known sources and identify target and suspect PFASs that can be used for source allocation.

An overview on human exposure, toxicity, solid-phase microextraction and adsorptive removal of perfluoroalkyl carboxylic acids (PFCAs) from water matrices

Perfluoroalkyl carboxylic acids (PFCAs) are sub-class of perfluoroalkyl substances commonly detected in water matrices. They are persistent in the environment, hence highly toxic to living organisms. Their occurrence at trace amount, complex nature and prone to matrix interference make their extraction and detection a challenge. This study consolidates current advancements in solid-phase extraction (SPE) techniques for the trace-level analysis of PFCAs from water matrices. The advantages of the methods in terms of ease of applications, low-cost, robustness, low solvents consumption, high pre-concentration factors, better extraction efficiency, good selectivity and recovery of the analytes have been emphasized. The article also demonstrated effectiveness of some porous materials for the adsorptive removal of the PFCAs from the water matrices. Mechanisms of the SPE/adsorption techniques have been discussed. The success and limitations of the processes have been elucidated.

Application of magnetic carbon nanotube composite nanospheres in magnetic solid-phase extraction of trace perfluoroalkyl substances from environmental water samples

The layer-by-layer assembly technique was used to synthesize novel multiwalled carbon nanotubes (MWCNTs) on magnetic carbon (Fe₃O₄@C) nanospheres, which were then used to extract six perfluoroalkyl substances (PFAS) in environmental real water samples using ultra high-performance liquid chromatography coupled to tandem mass spectrometry. The as-synthesized sorbent MWCNTs@Fe₃O₄@C was employed for magnetic solid-phase extraction (MSPE). The as-prepared MWCNTs@Fe₃O₄@C was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The main extraction parameters were systematically optimized by Box-Behnken design. Under optimal conditions, excellent results were achieved. The synthesized sorbent showed wide linear ranges (0.1-1000 ng L^-1), low detection limits (0.03-0.09 ng L^-1) and good repeatability (3.80%-9.52%) for extracting and detecting six PFAS. The developed method was also applied to analyze six PFAS from environmental water samples. This study indicated that MWCNTs@Fe₃O₄@C composites are promising materials for the extraction and determination of PFAS from water samples.

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.

Nontargeted screening reveals fluorotelomer ethoxylates in indoor dust and industrial wastewater

Concerns regarding the persistence, bioaccumulation behaviour, and toxicity of perfluorooctanoic acid and perfluorooctane sulfonic acid have resulted in the creation of thousands of replacement perfluoroalkyl substances (PFAS). This study reports on the discovery of fluorotelomer ethoxylates (FTEO) in indoor dust (9/15 samples), and industrial effluents (14/37 samples) using gas chromatographic cyclic ion mobility mass spectrometry (GC-cIMS). By filtering the detected unknowns by mass and collision-cross section, a series of FTEO homologues were revealed with the formula F-(CF₂)_n(C₂H₄O)_xH, where n = 6,8,10, and x = 4-12. The highest concentrations were observed in samples collected from healthcare facilities, consistent with the potential use of these compounds in anti-fog products, sprays used to prevent condensation on eyeglasses. FTEOs were also detected in c. 40 % of industrial effluent samples, with the highest concentrations in electroplating facilities, manufacturers of cosmetics and personal care products, and linen cleaning services for healthcare and work uniforms. These results suggest that FTEOs may well be widespread pollutants that are more persistent than previously thought, underlining the need for further study of their occurrence and potential impact to human health and the environment.

Occurrence, source apportionment, and pollution assessment of per- and polyfluoroalkyl substances in a river across rural and urban areas

Forty-three novel and legacy per- and polyfluoroalkyl substances (PFASs) in water and sediments from the Chaobai River (Beijing) were quantified. The total PFASs concentrations varied from 0.04 to 31.3 ng/L in water with significant spatial but insignificant seasonal variations, and changed from 0.03 to 4.29 ng/g in sediment with insignificant spatial but significant seasonal variations. The PFASs concentrations in water from the upstream across the rural area reflected the background level due to the extremely low concentration and very few detected PFASs. The consumer products and metal plating/textile were the predominant pollution sources of PFASs in winter and summer, respectively, for both water and sediment samples. Integrating the determined baseline value, the distribution of PFASs concentrations, and the ecological risks of PFASs, three criteria were proposed, which divide the PFASs concentrations in water into four pollution levels, i.e., insignificant, low, medium, and high. According to the suggested criteria, 96.4% of the PFASs levels in upstream was insignificant pollution, which decreased to 50.4% in downstream and 50.8% in reservoirs. The PFASs in China's and world's surface waters demonstrated similar pollution patterns, with PFOA, PFOS, and PFHxA being the top 3 polluted PFASs. This study makes a small step forward the development of water quality standard for PFASs, which is of great importance for pollution control and risk management of PFASs.

Occurrence, Distribution, and Environmental Behavior of Persistent, Mobile, and Toxic (PMT) and Very Persistent and Very Mobile (vPvM) Substances in the Sources of German Drinking Water

Persistent, mobile, and toxic (PMT) and very persistent and very mobile (vPvM) substances have been recognized as a threat to both the aquatic environment and to drinking water resources. These substances are currently prioritized for regulatory action by the European Commission, whereby a proposal for the inclusion of hazard classes for PMT and vPvM substances has been put forward. Comprehensive monitoring data for many PMT/vPvM substances in drinking water sources are scarce. Herein, we analyze 34 PMT/vPvM substances in 46 surface water, groundwater, bank filtrate, and raw water samples taken throughout Germany. Results of the sampling campaign demonstrated that known PMT/vPvM substances such as 1H-benzotriazole, melamine, cyanuric acid, and 1,4-dioxane are responsible for substantial contamination in the sources of German drinking water. In addition, the results revealed the widespread presence of the emerging substances 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and diphenylguanidine (DPG). A correlation analysis showed a pronounced co-occurrence of PMT/vPvM substances associated predominantly with consumer or professional uses and also demonstrated an inhomogeneous co-occurrence for substances associated mainly with industrial use. These data were used to test the hypothesis that most PMT/vPvM substances pass bank filtration without significant concentration reduction, which is one of the main reasons for introducing PMT/vPvM as a hazard class within Europe.

Trace determination of imidacloprid and its major metabolites in wheat-soil system

Trace analysis method is a reliable basis for studying the translocation and metabolism of imidacloprid used as an insecticide in wheat, and it clarifies whether biologically active metabolites including residual imidacloprid, have long-lasting insecticidal potency against wheat aphids under seed treatment during the entire growth period. In this study, a highly sensitive analytical method was established to determine the residues of imidacloprid and its six metabolites (5-hydroxy imidacloprid, imidacloprid olefin, imidacloprid guanidine, imidacloprid urea, 6-chloronicotinic acid and imidacloprid nitrosimine) in wheat-soil systems, such as in wheat leaves, wheat ears, wheat grains, roots and soil. All the compounds were extracted using an ACN:water (8:2, v/v) mixture and purified by dispersive solid-phase extraction. The average recoveries ranged from 74.4 to 109.5% for all matrices, with intra- and inter-day variations of less than 14.9%. The limit of quantitation was in the range of 0.001 to 0.005 mg/kg. The method is demonstrated to be sensitive and accurate for monitoring imidacloprid and its metabolites at trace levels during the entire growth period under field conditions. This article is protected by copyright. All rights reserved.

Long-term trends of fluorotelomer alcohols in a wastewater treatment plant impacted by textile manufacturing industry

Fluorotelomer alcohols (FTOHs) are important precursors and substitutes of perfluoroalkyl carboxylic acids (PFCAs). This study investigated the long-term trends of FTOHs in a municipal wastewater treatment plant impacted by textile manufacturing industry (T-WWTP) in Wuxi city from 2013 to 2021. For comparison, four domestic wastewater treatment plants (D-WWTPs) were also selected for the investigation. The total concentrations of FTOHs, which were 9.8-43 ng/L, 5.9-29 ng/L and 10-50 ng/g in influent, secondary effluent, and sludge samples from the T-WWTP, were significantly higher than those of the D-WWTPs (p < 0.01). The significant correlation between decrease of mass loads for FTOHs and the increase for PFCAs was observed, suggesting the potential biotransformation of FTOHs to PFCAs. Concentration variation in FTOH concentrations was observed for the T-WWTP, which was in accord with the variation in annual output of textile products in Wuxi city (p = 0.005). The predominance of 8:2 FTOH in the influents of T-WWTP between 2013 and 2016 switched over to 6:2 FTOH in 2020-2021. This work highlighted the textile manufacturing industry as a significant discharge route for FTOHs to municipal WWTP, as well as the dramatic change in the usage of FTOHs in the textile manufacturing industry in Wuxi.

Rapid quantitative analysis and suspect screening of per-and polyfluorinated alkyl substances (PFASs) in aqueous film-forming foams (AFFFs) and municipal wastewater samples by Nano-ESI-HRMS

A rapid analytical method for per- and polyfluoroalkyl substances (PFASs) combining nano-electrospray ionization and high-resolution mass spectrometry (Nano-ESI-HRMS) was developed and applied to aqueous film-forming foams (AFFFs) and wastewater samples collected from three local wastewater treatment plants (WWTPs). This method exhibited high sensitivity with lower limits of detection (LODs) of 3.2∼36.2 ng/L for 22 target PFAS analytes. In AFFF formulations, Nano-ESI-HRMS enabled the first-time detection of trifluoromethanesulfonic acid (TFMS), perfluoroethyl cyclohexanesulfonate (PFECHS), 6:2 fluorotelomer sulfonyl amido sulfonic acid (6:2 FTSAS-SO2), N-ammoniopropyl perfluoroalkanesulfonamidopropylsulfonate (N-AmP-FASAPS, n = 3-6), ketone-perfluorooctanesulfonic acid (Keto-PFOS), fluorotelomer unsaturated amide sulfonic acid (FTUAmS, n = 7), and 6:2 fluorotelomer amide (6:2 FTAm). Their structures were verified by the tandem MS analysis using collision-induced dissociation. Further, the combination of absolute and semi-quantification results revealed 16 PFASs from 9 PFAS classes as dominant AFFF constituents, accounting for 88.2∼96.5% of the total detected anionic and zwitterionic PFASs, including perfluorinated sulfonic acids (PFSAs, n = 1,4∼8), 6:2 fluorotelomer sulfonates (6:2 FTS), fluorotelomer thioether amido sulfonic acid (FTSAS, n = 6,8), fluorotelomer sulfinyl amido sulfonic acid (FTSAS-SO, n = 6,8), N-AmP-FASAPS (n = 6), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), perfluoroalkylsulfonamido amino carboxylate (PFASAC, n = 6), 2-((perfluorooctyl)thio)acetatic acid (Thio-8:2 FTCA), and 6:2 FTAm. At WWTPs, aerobic and anaerobic biotransformation of PFAS precursors at the aeration tanks and secondary clarifiers were evident by the generation of mid/short-chain perfluoroalkyl acids, such as perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), as well as the emergence of ultrashort trifluoroacetic acid (TFA) and TFMS and several novel fluorotelomer carboxylic acids (FTCAs). Overall, Nano-ESI-HRMS enabled comprehensive PFAS quantitative analysis and suspect screening, applicable for rapid investigation and assessment of PFAS-related exposure and treatment in environmental matrixes. Our results also revealed that AFFFs and municipal wastewaters are two key sources contributing to the prevalent detection of ultrashort-chain PFASs (e.g., TFMS and TFA) in water.

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.

Nano-enabled sensing of per-/poly-fluoroalkyl substances (PFAS) from aqueous systems - A review

Per-/poly-fluoroalkyl substances (PFAS) are an emerging class of environmental contaminants used as an additive across various commodity and fire-retardant products, for their unique thermo-chemical stability, and to alter their surface properties towards selective liquid repellence. These properties also make PFAS highly persistent and mobile across various environmental compartments, leading to bioaccumulation, and causing acute ecotoxicity at all trophic levels particularly to human populations, thus increasing the need for monitoring at their repositories or usage sites. In this review, current nano-enabled methods towards PFAS sensing and its monitoring in wastewater are critically discussed and benchmarked against conventional detection methods. The discussion correlates the materials' properties to the sensitivity, responsiveness, and reproducibility of the sensing performance for nano-enabled sensors in currently explored electrochemical, spectrophotometric, colorimetric, optical, fluorometric, and biochemical with limits of detection of 1.02 × 10^-6 μg/L, 2.8 μg/L, 1 μg/L, 0.13 μg/L, 6.0 × 10^-5 μg/L, and 4.141 × 10^-7 μg/L respectively. The cost-effectiveness of sensing platforms plays an important role in the on-site analysis success and upscalability of nano-enabled sensors. Environmental monitoring of PFAS is a step closer to PFAS remediation. Electrochemical and biosensing methods have proven to be the most reliable tools for future PFAS sensing endeavors with very promising detection limits in an aqueous matrix, short detection times, and ease of fabrication.

PFAS Analysis with Ultrahigh Resolution 21T FT-ICR MS: Suspect and Nontargeted Screening with Unrivaled Mass Resolving Power and Accuracy

Per- and polyfluoroalkyl substances (PFASs) are a large family of thousands of chemicals, many of which have been identified using nontargeted time-of-flight and Orbitrap mass spectrometry methods. Comprehensive characterization of complex PFAS mixtures is critical to assess their environmental transport, transformation, exposure, and uptake. Because 21 tesla (T) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest available mass resolving power and sub-ppm mass errors across a wide molecular weight range, we developed a nontargeted 21 T FT-ICR MS method to screen for PFASs in an aqueous film-forming foam (AFFF) using suspect screening, a targeted formula database (C, H, Cl, F, N, O, P, S; ≤865 Da), isotopologues, and Kendrick-analogous mass difference networks (KAMDNs). False-positive PFAS identifications in a natural organic matter (NOM) sample, which served as the negative control, suggested that a minimum length of 3 should be imposed when annotating CF₂-homologous series with positive mass defects. We putatively identified 163 known PFASs during suspect screening, as well as 134 novel PFASs during nontargeted screening, including a suspected polyethoxylated perfluoroalkane sulfonamide series. This study shows that 21 T FT-ICR MS analysis can provide unique insights into complex PFAS composition and expand our understanding of PFAS chemistries in impacted matrices.

Impairment of human dopaminergic neurons at different developmental stages by perfluoro-octanoic acid (PFOA) and differential human brain areas accumulation of perfluoroalkyl chemicals

Perfluoroalkyl substances (PFASs) are synthetic chemicals widely used in industrial and consumer products. The environmental spreading of PFASs raises concerns for their impact on human health. In particular, the bioaccumulation in humans due to environmental exposure has been reported also in total brain samples and PFAS exposure has been associated with neurodevelopmental disorders. In this study we aimed to investigate the specific PFAS bioaccumulation in different brain areas. Our data reported major accumulation in the brainstem region, which is richly populated by dopaminergic neurons (DNs), in brain autopsy samples from people resident in a PFAS-polluted area of Italy. Since DNs are the main source of dopamine (DA) in the mammalian central nervous system (CNS), we evaluated the possible functional consequences of perfluoro-octanoic acid (PFOA) exposure in a human model of DNs obtained by differentiation of human induced pluripotent stem cells (hiPSCs). Particularly, we analyzed the specific effect of the exposure to PFOA for 24 h, at the concentration of 10 ng/ml, at 3 different steps of dopaminergic differentiation: the neuronal commitment phase (DP1), the neuronal precursor phase (DP2) and the mature dopaminergic differentiation phase (DP3). Interestingly, compared to untreated cells, exposure to PFOA was associated with a reduced expression of Tyrosine Hydroxylase (TH) and Neurofilament Heavy (NFH), both markers of dopaminergic maturation at DP2 phase. In addition, cells at DP3 phase exposed to PFOA showed a severe reduction in the expression of the Dopamine Transporter (DAT), functionally involved in pre-synaptic dopamine reuptake. In this proof-of-concept study we show a significant impact of PFOA exposure, mainly on the most sensitive stage of neural dopaminergic differentiation, prompting the way for further investigations more directly relevant to risk assessment of these chemicals.

Insights on preparation, structure and activities of Gracilaria lemaneiformis polysaccharide

Gracilaria lemaneiformis is a kind of edible economic red algae, which is rich in polysaccharide, phycobiliprotein, pigments, minerals and other nutrients and functional components. Polysaccharide is one of the main active components of Gracilaria lemaneiformis, which has been reported to present various physiological bioactivities, including regulation of glycolipid metabolism, immune, anti-tumor, anti-inflammatory and other biological activities. This paper aims to provide a brief summary of extraction, purification, structural characteristics, and physiological activities of Gracilaria lemaneiformis polysaccharide (GLP). This article is able to provide theoretical basis for the future research and exploitation of GLP, and improve its potential development to promote the healthy and sustainable processing and high value utilization industry of Gracilaria lemaneiformis.

Occurrence and removal of poly/perfluoroalkyl substances (PFAS) in municipal and industrial wastewater treatment plants

The presence of poly- and perfluoroalkyl substances (PFAS) has caused serious problems for drinking water supplies especially at intake locations close to PFAS manufacturing facilities, wastewater treatment plants (WWTPs), and sites where PFAS-containing firefighting foam was regularly used. Although monitoring is increasing, knowledge on PFAS occurrences particularly in municipal and industrial effluents is still relatively low. Even though the production of C8-based PFAS has been phased out, they are still being detected at many WWTPs. Emerging PFAS such as GenX and F-53B are also beginning to be reported in aquatic environments. This paper presents a broad review and discussion on the occurrence of PFAS in municipal and industrial wastewater which appear to be their main sources. Carbon adsorption and ion exchange are currently used treatment technologies for PFAS removal. However, these methods have been reported to be ineffective for the removal of short-chain PFAS. Several pioneering treatment technologies, such as electrooxidation, ultrasound, and plasma have been reported for PFAS degradation. Nevertheless, in-depth research should be performed for the applicability of emerging technologies for real-world applications. This paper examines different technologies and helps to understand the research needs to improve the development of treatment processes for PFAS in wastewater streams.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs): An optimized LC-MS/MS procedure for feed analysis

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are extremely stable highly fluorinated aliphatic compounds, widely used in chemical and industrial applications since 1950s. They are ubiquitously detected in the environment and diet is the main route for human exposure. To ensure human safety, it is necessary to follow the whole food production chain, including animal feed. Still PFASs are not regulated as undesirable substances in feed, although several studies have shown they can be transferred from feed to livestock and thereafter to food. This paper describes the development, optimization and the full validation of a sensitive and reliable analytical protocol enabling the quantification of 19 PFASs in animal feeds by liquid chromatography - mass spectrometry (LC-MS/MS). The method was optimized, assessing the possible matrix interferences, and submitted to comprehensive validation (55 independent spiking experiments). Validation experiments were conducted on blank fish feed samples (natural levels of PFASs < 0.10 ng g^-1) spiked at five different concentrations (0.10, 0.50, 1.0, 5.0 and 10 ng g^-1). Apparent recoveries (R%) were generally between 88 and 111%; R% < 80% were obtained only at the lower validation levels for those molecules not having the corresponding labelled analogues. Relative standard deviations in repeatability conditions (RSDr) and within-lab reproducibility conditions (RSDw_R) were lower or equal to 11% and 22% respectively. Limits of quantification were set for most of the analytes at 0.10 ng g^-1 (LOQs) and verified with repeated analysis on fortified samples (0.10 ng g^-1). Limits of detection (LODs) were calculated as 1/3 LOQ. Finally the method was applied to 23 feed samples of different type (compound feed, vegetable feed material, complementary feed, pre-mixture and mineral feed) and all of them did not show PFAS above LOQ.

A review of the occurrence, transformation, and removal of poly- and perfluoroalkyl substances (PFAS) in wastewater treatment plants

Poly- and perfluoroalkyl substances (PFAS) comprise more than 4,000 anthropogenically manufactured compounds with widescale consumer and industrial applications. This critical review compiles the latest information on the worldwide distribution of PFAS and evaluates their fate in wastewater treatment plants (WWTPs). A large proportion (>30%) of monitoring studies in WWTPs were conducted in China, followed by Europe (30%) and North America (16%), whereas information is generally lacking for other parts of the world, including most of the developing countries. Short and long-chain perfluoroalkyl acids (PFAAs) were widely detected in both the influents (up to 1,000 ng/L) and effluents (15 to >1,500 ng/L) of WWTPs. To date, limited data is available regarding levels of PFAS precursors and ultra-short chain PFAS in WWTPs. Most WWTPs exhibited low removal efficiencies for PFAS, and many studies reported an increase in the levels of PFAAs after wastewater treatment. The analysis of the fate of various classes of PFAS at different wastewater treatment stages (aerobic and/aerobic biodegradation, photodegradation, and chemical degradation) revealed biodegradation as the primary mechanism responsible for the transformation of PFAS precursors to PFAAs in WWTPs. Remediation studies at full scale and laboratory scale suggest advanced processes such as adsorption using ion exchange resins, electrochemical degradation, and nanofiltration are more effective in removing PFAS (~95-100%) than conventional processes. However, the applicability of such treatments for real-world WWTPs faces significant challenges due to the scaling-up requirements, mass-transfer limitations, and management of treatment by-products and wastes. Combining more than one technique for effective removal of PFAS, while addressing limitations of the individual treatments, could be beneficial. Considering environmental concentrations of PFAS, cost-effectiveness, and ease of operation, nanofiltration followed by adsorption using wood-derived biochar and/or activated carbons could be a viable option if introduced to conventional treatment systems. However, the large-scale applicability of the same needs to be further verified.

Development of a magnetic MOF-based M-D-μSPE methodology combined with LC-MS/MS for the determination of fluorotelomer alcohols and its metabolites in animal derived foods

In this study, a novel modified metal organic framework (MOF) was prepared and used as adsorbent of miniaturized solid-phase extraction (M-D-μSPE) for analyzing 8-2 FTOH and its metabolites in edible tissues by LC-MS/MS. This synthesized adsorbent, named as Fe₃O₄@Fe-MIL 101-NH₂ (magnetic Fe-MOF), was characterized. Moreover, the effects factors on the adsorption behavior of the adsorbents for the analytes were investigated and optimized in detail, such as solution pH, adsorbent amount, extraction time, desorption condition. The adsorbtion mechanism of magnetic Fe-MOF might be electrostatic interaction, CF-π hydrophobic and Lewis acid base. Compared with conventional adsorbents (such as PSA, C18), magnetic Fe-MOF reduced matrix effect. The limits of quantification ranged 0.10-1.5 µg/kg. The recoveries of analytes ranged 78.0% - 90.3% in spiked samples, with relative standard deviations less than 12.0%. The developed method was successfully utilized to analyze incurred samples, which proves that it is a rapid, efficient, and sensitive method.

Room-temperature synthesis of amino-functionalized magnetic covalent organic frameworks for efficient extraction of perfluoroalkyl acids in environmental water samples

The novel amino-functionalized magnetic covalent organic framework nanocomposites (Fe₃O₄@[NH₂]-COFs) were fabricated at room temperature, which were explored as a magnetic adsorbent for magnetic solid-phase extraction (MSPE). On the basis of the hydrophobic surfaces of magnetic nanocomposites and introduction of primary amines into the COFs shell, Fe₃O₄@[NH₂]-COFs displayed excellent enrichment capacity in "catching" ultratrace perfluoroalkyl acids (PFAAs) from water samples because of the synergistic combination of hydrophobic and electrostatic interactions between PFAAs and Fe₃O₄@[NH₂]-COFs. Under the optimized pretreatment and instrumental parameters, the proposed pretreatment approach, which hybridized MSPE using Fe₃O₄@[NH₂]-COFs and HPLC-MS/MS, displayed favorable linearity (10-10,000 ng L^-1) with R² (0.9990-0.9999), low limits of detection (0.05-0.38 ng L^-1), and excellent repeatability (3.7-9.2%). Moreover, the established approach was successfully utilized to determine PFAAs in real water samples with spiked recoveries ranging from 72.1% to 115.4%. Results indicated that Fe₃O₄@[NH₂]-COFs would be a potential alternative for MSPE of PFAAs at ultra-low levels.

Analysis of 58 poly-/perfluoroalkyl substances and their occurrence in surface water in a high-technology industrial park

Poly/perfluoroalkyl substances (PFASs) have some water solubility so that they are more liable to enter surface water. A comprehensive analysis method was established to analyze 17 classes of 58 PFASs in surface water by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) after automated solid phase extraction (SPE). The method showed acceptable recoveries and precision with recoveries of 60%-130% and RSD less than 30% with a few exceptions, and method detection limits (MDLs) of 0.004 ng/L-2.0 ng/L. It was investigated the surface water around Zhangjiang High-Technology Park in Shanghai. The concentration of ∑PFASs ranged from 115 ng/L to 600 ng/L. The main pollutant was perfluoro-3-methylheptanoic acid (P3MHpA), which is isopropyl isomer of perfluorooctanoic acid (PFOA), accounting 41.6% of ∑PFASs. It was detected in all samples and its level was far higher than that of PFOA with the maximum of 432 ng/L determined surrounding integrated circuits company. Short-chain perfluorocarboxylic acids (PFCAs) and PFOA were also major constituents accounting for 39.9% of ∑PFASs. Perfluorosulfonic acid (PFSAs (C_{4, 6, 8})) were detected in all samples, while most concentrations were below 10 ng/L. In addition, 1H,1H,2H,2H-perfluorooctane sulfonate (6:2) (6:2 FTS), 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoic acid (HFPO-DA) and 9-chlorohexadecafluoro-3-oxanonane-sulfonate (9Cl-PF3ONS) were also detected in all samples at low level. Long chain PFCAs and PFSAs and other classes of PFASs were also detected with low levels and/or low frequencies. The level of PFASs shows an increasing trend in surface water in Shanghai. The whole risk is low for residents from water exposure, while it should cautious to the emission of P3MHpA from integrated circuits and its potential risk.

β-Cyclodextrin Polymers with Different Cross-Linkers and Ion-Exchange Resins Exhibit Variable Adsorption of Anionic, Zwitterionic, and Nonionic PFASs

Per- and polyfluoroalkyl substances (PFASs) occur in groundwater as mixtures of anionic, cationic, zwitterionic, and nonionic species, although few remediation technologies have been evaluated to assess the removal of different types of PFASs. In this study, we evaluated the performance of three β-cyclodextrin polymers (CDPs), an anion-exchange (AE) resin, and a cation-exchange (CE) resin for the removal of anionic, zwitterionic, and nonionic PFASs from water. We found that a CDP with a negative surface charge rapidly removes all zwitterionic PFASs with log K_D values ranging between 2.4 and 3.1, and the CE resin rapidly removes two zwitterionic PFASs with log K_D values of 1.8 and 1.9. The CDPs with a positive surface charge rapidly remove all anionic PFASs with log K_D values between 2.7 and 4.1, and the AE resin removes all anionic PFASs relatively slowly with log K_D values between 2.0 and 2.3. All adsorbents exhibited variable removal of the nonionic PFASs and some adsorption inhibition at higher pH values and in the presence of groundwater matrix constituents. Our findings provide insight into how adsorbents can be combined to remediate groundwater contaminated with complex mixtures of different types of PFASs.

Rapid microwave synthesis of dioxin-linked covalent organic framework for efficient micro-extraction of perfluorinated alkyl substances from water

To synthesize covalent organic framework (COF) via irreversible reactions is more challenging than by reversible ones. In this work, microwave-assisted synthesis is used to facilitate the nucleophilic substitution of 2,3,5,6-tetrafluoro-4-pyridinecarbonitrile with 2,3,6,7,10,11-hexahydroxy triphenylene. The dioxin-linked COF, named TH-COF, was efficiently synthesized with extraordinarily large surface area of 1254 m² g^-1. With its high crystallinity, excellent thermal and chemical stabilities, TH-COF is used as the coating for the solid-phase micro-extraction (SPME) of perfluorinated alkyl substances (PFASs). The adsorptive mechanism was evaluated with adsorption isotherm and kinetic adsorption. Adsorption energies are calculated based on the density functional theory. Following SPME with TH-COF-coated fibers, PFASs were eluted using 1 mL of 0.6% trifluoroacetic acid/methanol and analyzed through the ultra-performance liquid chromatography equipped with triple quadrupole mass spectrometer (UPLC-MS/MS). When applied to spiked real water samples, this method demonstrates good linearity (0.01-1000 ng L^-1) with R² ≥ 0.9945. The TH-COF-SPME-UPLC-MS/MS technique provides low limits of detection (0.0020-0.0045 ng L^-1), excellent precision (≤ 7.9%), and good fiber-to-fiber reproducibility (≤ 7.1%). The TH-COF-coated fibers can be reused at least 20 times without the loss of extraction performance. In addition, the relative recoveries from spiked real water samples are 89.5%-105%.

Detection of perfluorooctane sulfonate by ion-transfer stripping voltammetry at an array of microinterfaces between two immiscible electrolyte solutions

Per- and polyfluoroalkyl substances (PFAS) are a category of persistent environmental contaminants that have been linked to health issues in humans. In this work, we investigate the detection of perfluorooctanesulfonate (PFOS-), one such PFAS, by ion-transfer voltammetry at an array of microinterfaces between two immiscible electrolyte solutions (μITIES). Cyclic voltammetry, differential pulse voltammetry and differential pulse stripping voltammetry (DPSV) indicated the ion-transfer behaviour and detection of PFOS-, with the latter enabling detection at picomolar concentrations. Using a 5 min preconcentration time, during which PFOS- was preconcentrated into the organic phase of the μITIES array, a limit of detection (LOD) of 0.03 nM (0.015 μg L-1) in aqueous electrolyte was achieved. This performance is attributed to the enhanced mass transport (radial diffusion) to the μITIES that occurs during preconcentration. To investigate the potentiality for applications of this analytical approach to environmental samples, measurements in a range of water matrices were investigated. Drinking water, laboratory tap water and seawater matrices were assessed by spiking with PFOS- over the 0.1-1 nM range. A matrix effect was observed, with changes in sensitivity and LOD relative to those in pure aqueous electrolyte solutions. Such matrix effects need to be considered in designing applications of these PFOS- measurements to environmental samples. The results presented here indicate that DPSV at a μITIES array can form the basis for a fast and sensitive screening method for PFOS- contamination that is suited to portable and on-site applications.

A sensitive method for simultaneous determination of 12 classes of per- and polyfluoroalkyl substances (PFASs) in groundwater by ultrahigh performance liquid chromatography coupled with quadrupole orbitrap high resolution mass spectrometry

Per- and polyfluoroalkyl substances (PFASs) comprise a large group of chemicals with diverse physicochemical properties, which make their simultaneous determination a challenging task. A trace analytical method based on ultrahigh performance liquid chromatography-quadrupole Orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) was developed for simultaneous determination of 54 PFASs belonging to 12 classes in groundwater, including 24 perfluorocarbons and 30 precursors. This method provided good linearity of calibration standards (R² > 0.99), excellent method limits of quantification (MLOQs) (0.5-250 pg/L), satisfactory matrix spiking recoveries (63%-148%), high precision (intra-day relative standard deviations (RSDs) 1.4-11.4%, inter-day RSDs 1.6-12.9%, and inter-week RSDs 2.1-12.7%), and short runtime (13 min), suitable for high throughput studies. The newly established method was successfully applied to detect PFASs in the groundwater samples collected from Hebei Province, China. Twenty PFASs were detected with the total concentration of 0.3-32.9 ng/L, indicating the contamination level similar to that in drinking water. The dominant PFASs were perfluorobutanesulfonate (PFBS), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA) and perfluorooctanoic acid (PFOA). In addition, 6:2 fluorotelomer phosphate diester (6:2 diPAP) and 6:2 fluorotelomer sulfonate (6:2 FTS) were found as the major precursors. The total PFAS concentrations were lower than the cumulative permissible limit of 70 ng/L for PFOS and PFOA recommended by the United States Environmental Protection Agency (USEPA) for drinking water in 2016. In a nutshell, this study provided a fast and sensitive method based on HRMS for the simultaneous analysis of a wide range of PFASs, present at trace levels in groundwater samples.

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.

Emerging per- and polyfluoroalkyl substances (PFASs) in surface water and sediment of the North and Baltic Seas

Along with the phase-out of legacy long-chain perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane sulfonic acids (PFSAs) and their precursors, attention has been drawn to emerging per- and polyfluoroalkyl substances (PFASs). This study is aimed at investigating the importance of selected emerging PFASs as pollutants in European coastal environments and a possible transition from legacy long-chain PFCAs and PFSAs to replacement compounds. Therefore, the spatial distribution of 29 PFASs was analysed in surface water and sediment of the North and Baltic Seas sampled in 2017. Levels of the replacement compound HFPO-DA were approximately three times higher than those of its predecessor PFOA in surface water from the North Sea, which is characterised by the influence of point sources and constant exchange with open water. Reanalysis of sample extracts from the last decade showed that HFPO-DA had already been present in 2011, when it had not yet been in focus. In the Baltic Sea with a limited water exchange and dominance of diffuse sources, the proportion of HFPO-DA was negligible, whereas long-chain PFCAs and PFSAs still contributed to ∑PFASs with about 30%. The emerging cyclic compound perfluoro-4-ethylcyclohexanesulfonate (PFECHS), which has not yet been reported in European coastal environments, was detected in 86% of the Baltic Sea samples. Influenced by sediment characteristics in addition to source-specific contributions, the spatial distribution of PFASs in surface sediments was more variable than for water samples. The linear isomer of the long-chain legacy substance PFOS was the predominant compound found over the entire study area. Of the emerging PFASs, 6:6 and 6:8 perfluoroalkyl phosphinic acids (PFPiAs) were identified close to potential industrial inputs and in sedimentation areas. The results show that particular emerging PFASs play a relevant role in the investigated coastal environments and that a shift to replacements is dependent on sources and geographical conditions.

A single analytical method for the determination of 53 legacy and emerging per- and polyfluoroalkyl substances (PFAS) in aqueous matrices

A quantitative method for the determination of per- and polyfluoroalkyl substances (PFAS) using liquid chromatography (LC) tandem mass spectrometry (MS/MS) was developed and applied to aqueous wastewater, surface water, and drinking water samples. Fifty-three PFAS from 14 compound classes (including many contaminants of emerging concern) were measured using a single analytical method. After solid-phase extraction using weak anion exchange cartridges, method detection limits in water ranged from 0.28 to 18 ng/L and method quantitation limits ranged from 0.35 to 26 ng/L. Method accuracy ranged from 70 to 127% for 49 of the 53 extracted PFAS, with the remaining four between 66 and 138%. Method precision ranged from 2 to 28% RSD, with 49 out of the 53 PFAS being below < 20%. In addition to quantifying > 50 PFAS, many of which are currently unregulated in the environment and not included in typical analytical lists, this method has efficiency advantages over other similar methods as it utilizes a single chromatographic separation with a shorter runtime (14 min), while maintaining method accuracy and stability and the separation of branched and linear PFAS isomers. The method was applied to wastewater influent and effluent; surface water from a river, wetland, and lake; and drinking water samples to survey PFAS contamination in Australian aqueous matrices. The compound classes FTCAs, FOSAAs, PFPAs, and diPAPs were detected for the first time in Australian WWTPs and the method was used to quantify PFAS concentrations from 0.60 to 193 ng/L. The range of compound classes detected and different PFAS signatures between sample locations demonstrate the need for expanded quantitation lists when investigating PFAS, especially newer classes in aqueous environmental samples. Graphical abstract.

The overlooked short- and ultrashort-chain poly- and perfluorinated substances: A review

Poly- and perfluorinated substances (PFAS) comprise more than 3000 individual compounds; nevertheless, most studies to date have focused mainly on the fate, transport and remediation of long-chain PFAS (C > 7). The main objective of this article is to provide the first critical review of the peer-reviewed studies on the analytical methods, occurrence, mobility, and treatment for ultra-short-chain PFAS (C = 2-3) and short-chain PFAS (C = 4-7). Previous studies frequently detected ultra-short-chain and short-chain PFAS in various types of aqueous environments including seas, oceans, rivers, surface/urban runoffs, drinking waters, groundwaters, rain/snow, and deep polar seas. Besides, the recent regulations and restrictions on the use of long-chain PFAS has resulted in a significant shift in the industry towards short-chain alternatives. However, our understanding of the environmental fate and remediation of these ultra-short-chain and short-chain PFAS is still fragmentary. We have also covered the handful studies involving the removal of ultra-short and short-chain PFAS and identified the future research needs.

Development of a UHPLC-MS method for inhibitor screening against α-L-1,3-fucosidase

α-L-Fucosidase (AFU) is a promising therapeutic target for the treatment of inflammation, cancer, cystic fibrosis, and fucosidosis. Some of the existing analytical methods for the assessment of AFU activity are lacking in sensitivity and selectivity, since most of them are based on spectrofluorimetric methods. More recently, mass spectrometry (MS) has evolved as a key technology for enzyme assays and inhibitor screening as it enables accurate monitoring of the conversion of substrate to product in enzymatic reactions. In this study, UHPLC-MS has been utilized to develop a simple, sensitive, and accurate assay for enzyme kinetics and inhibition studies of AFU3, a member of the AFU family. A reported method for analyzing saccharide involving a porous graphitic carbon column, combined with reduction by NaBH₄/CH₃OH, was used to improve sensitivity. The conversion of saccharide into alditol could reach nearly 100% in the NaBH₄ reduction reaction. In addition, the bioanalytical quantitative screening method was validated according to US-FDA guidance, including selectivity, linearity, precision, accuracy, stability, and matrix effect. The developed method displayed a good accuracy, high sensitivity (LOD = 0.05 mg L^-1), and good reproducibility (RSD < 15%). The assay accurately measured an IC₅₀ value of 0.40 μM for the known AFU inhibitor, deoxyfuconojirimycin, which was consistent with results reported in the literature. Further validation of the assay was achieved through the determination of a high Z'-factor value of 0.89. The assay was applied to screen a marine-derived chemical library against AFU3, which revealed two marine-oriented pyrimidine alkaloids as potential AFU3 inhibitors. Graphical abstract.

Determination of 23 perfluorinated alkylated substances in water and suspended particles by ultra-performance liquid chromatography/tandem mass spectrometry

A practical multi-residue method based on ultra-performance liquid chromatography/tandem mass spectrometry was developed for the simultaneous determination of 23 perfluorinated alkylated substances (PFASs) in water and suspended particles. Suspended particle samples were extracted with 1% formic acid-acetonitrile and cleaned by matrix solid phase dispersion extraction using a C₁₈ sorbent and graphitized carbon black. Water samples were filtered through 0.7-μm glass fiber membranes and enriched utilizing weak anion exchange cartridges. The eluent was dried under a gentle stream of N₂ at 45°C and suspended in 1 mL acetonitrile-5 mM ammonium acetate (1:1, vol:vol). Gradient elution for chromatographic separation utilized acetonitrile and 5 mM ammonium acetate as mobile phases on a reverse phase C₁₈ column. The compounds were quantified using an internal standard method in multiple reaction-monitoring mode. Limits of detection and quantitation of the 23 PFAS test compounds in water samples were 0.5-10 ng L^-1 and 2-20 ng L^-1, respectively. Recoveries at three fortified levels of 20, 50, and 200 ng L^-1 ranged from 68.5% to 118% with relative standard deviations below 9.6%. We used this method to determine PFAS levels in real water and suspended particle samples and found high sensitivity and good reproducibility.

Perfluoroalkyl phosphonic acids adsorption behaviour and removal by wastewater organisms

In this study we have experimentally assessed different physicochemical parameters such as the distribution constant between octanol - water and between water and sludge for three perfluoroakyl substances (PFASs) widely used in waxes and coating materials: perfluorohexane (PFHxPA), perfluorooctane (PFOPA) and perfluorodecane (PFDPA) phosphonic acids. Distribution coefficients were assessed based on the procedures described in the OECD guideline 123 for partition coefficients while the studies of adsorption-desorption in sludge based on the indirect method of the OECD guideline 106. Besides, the removal behaviour of selected compounds has been evaluated using the green algae Desmodesmus subspicatus and microorganisms present in an effluent wastewater. These last experiments were carried out using laboratory scale bioreactors under aerobic conditions according to the OECD guideline 309. The main results of this study showed the resistance to biodegradation of selected compounds by both treatments, <5% was eliminated using D. subspicatus and similar results were obtained by aerobic degradation with wastewater microorganisms. However, it was observed that PFDPA induced changes in algae colour while it was detected to be accumulated in a floccula generated by the microorganisms present in wastewater. According to distribution coefficients the three compounds have values of logD_ow below 3, indicating their capability to be present in both phases. Finally, the results of the adsorption/desorption experiments showed that PFOPA and PFDPA reach the equilibrium after 10 days of contact with a sorption percentage higher than 40% and 70%, respectively.