Investigation of the adsorption/desorption mechanism of perfluoroalkyl substances on HLB-WAX extraction phases for microextraction

Targeted determination of volatile fluoroalkyl pollutants and non-targeted screening for environmental monitoring

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants known for their toxicity, mobility, and bioaccumulation. Efficient sample preparation and analysis of these compounds are critical for environmental monitoring. In this study, a novel analytical methodology is presented, integrating dynamic headspace extraction (DHS) and thermal desorption (TD) with one-dimensional (1D) and two-dimensional (2D) gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) for the quantification of target volatile and semi-volatile PFAS. Such an approach also enables the non-targeted screening of other classes of contaminants in aqueous samples. The method was optimized and validated for nine (semi-)volatile PFAS, including fluorotelomer alcohols (FTOHs), acrylate (FTAc), and alkyl sulfonamides (FOSA, FOSE). Three types of adsorbent materials were evaluated during the enrichment step, among which Tenax TA demonstrated superior recovery and reproducibility. Extraction volumes of 1 L, 2 L, and 5 L were tested, with 1 L providing the most consistent recoveries and reproducibility. The optimized method achieved detection limits as low as 2.17 ng L-1, indicating high sensitivity. In a case study involving water from an industrial site, the enhanced separation and detection capabilities of GC×GC-TOFMS enabled the identification of 115 additional environmentally relevant compounds, including halogen-containing compounds, monoaromatics, and polycyclic aromatic hydrocarbons. This integrated DHS-TD-GC×GC-TOFMS approach provides a robust and suitable analytical solution for targeted PFAS monitoring, combining high sensitivity and selectivity with simultaneous non-targeted analytical capabilities - a particularly advantageous feature for the environmental monitoring of (semi-)volatile chemicals in real samples.

Solid-phase microextraction with recessed matrix compatible coating for in situ sampling of per- and polyfluoroalkyl substances in meat

This study presents a novel method for in situ extraction of per- and polyfluoroalkyl substances (PFAS) from intact meat samples using a recessed solid phase microextraction (SPME) device coupled with LC-MS/MS. The SPME device with matrix-compatible coating (HLB-WAX/PAN) in the recessed section, exhibited mechanically robust and low matrix effects in meat samples (-13.7-11.1 %). Key parameters influencing extraction efficiency, including extraction time, adsorbent amount, extraction temperature, and desorption time were comprehensively optimized. The stability of PFAS adsorbed onto the coating during storage at different temperatures and durations was also assessed. Under optimized conditions, the proposed method demonstrated applicability across pork, beef, and lamb tissues with excellent linearity (R2 ≥ 99.32 %), good sensitivity (LOD in the range of 0.01-1.52 ng/g), as well as acceptable accuracy and reproducibility (intra-day and inter-day). Compared with conventional methods, the SPME-LC-MS/MS method shows the advantages of simple operation, short extraction time and low organic solvent consumption with low matrix effects. This approach offers a straightforward and reliable solution for direct in situ monitoring PFAS in commercial meat samples and has potential for on-site application.

Practicality evaluation of novel microextraction techniques for the determination of PFAS in food and water samples using the Blue Applicability Grade Index

BACKGROUND

Due to their high stability, persistence, and non-degradability, per- and polyfluoroalkyl substances (PFAS) are considered to be "forever chemicals" that can be present in a wide range of samples. Towards the development of novel analytical strategies for the reduction of the environmental impact of the analytical scheme, a plethora of novel solid-phase microextraction and miniaturized extraction techniques have been proposed for the determination of PFAS. However, the evaluation of the applicability of these protocols in terms of their practicality is still scarce.

RESULTS

In this article, the Blue Analytical Grade Index (BAGI) was used to evaluate the practicality of the sorbent-based microextraction techniques that were developed during the last decade for PFAS. In total thirty-four protocols were evaluated, resulting in a minimum score of 50.0 and a maximum score of 77.5.

SIGNIFICANCE

These findings clearly indicate that there is significant room for improvement and there is still a need for the development of microextraction approaches with higher practicality. Moreover, with regards to the best-performing protocols, their greenness was also assessed using the AGREEprep metric to enable a more comprehensive comparison.

High-Throughput Screening of Polyfluoroalkyl Substances Using Solid-Phase Microextraction Coupled to Microfluidic Open Interface-Mass Spectrometry

Efficient and sustainable methods for large-scale PFAS monitoring are critical for addressing environmental and public health challenges. This work presents a high-throughput sample preparation system capable of processing up to 48 samples simultaneously using solid-phase microextraction (SPME) and was directly coupled with mass spectrometry (MS) via an automated microfluidic open interface (MOI), bypassing the need for chromatographic separation. The SPME-MOI-MS approach achieves sensitive detection of 18 PFAS in drinking water, with limits of detection (LODs) between 1 and 10 pg/mL, using just 1.5 mL of sample and an average analysis time of 2.8 min per sample. The SPME blades, employed to enhance sensitivity in place of standard SPME fibers, incorporate a matrix-compatible coating material that enables effective PFAS screening in water as well as complex matrices including blood, beer, and beef. In addition, significantly low recovery and reproducibility of nonpolar PFAS in water analysis have been found and studied, indicating that using a glass container and adding a small percentage of acetonitrile can address this issue.

Enhancing the Separation and Quantification of Perfluoroalkyl Substances Using Polymeric Ionic Liquid Sorbents in Thin Film Microextraction

The preconcentration and isolation of per- and polyfluoroalkyl substances (PFAS) remain challenging due to their varying chain lengths and diverse headgroup chemical functionalities. These substances are persistent and occur in the environment at low parts-per-trillion concentration levels, necessitating the use of efficient and selective sorbents that can enhance their preconcentration from the targeted sample prior to instrumental analysis. This study, for the first time, evaluates the use of a polymeric ionic liquid (PIL) consisting of 1-(9-carboxy-nonyl)-3-vinylimidazolium bromide [C9COOHVim+] [Br-] ionic liquid (IL) monomer and 1,12-di(3-vinylimidazolium)dodecane bromide ([C12(Vim+)2]2[Br-]) IL cross-linker for the simultaneous separation and preconcentration of 15 anionic PFAS. The PIL was immobilized on a thin film microextraction device to improve preconcentration, extraction, and desorption kinetics. The addition of competing anions to the desorption solution was critical to ensure the quantitative desorption of the anionic PFAS by an ion exchange mechanism. Partition coefficient calculations revealed a balanced extraction coverage for short- and long-chain PFAS in ultrapure water, while in solutions at high ionic strength, short-chain PFAS tend to display less affinity for the sorbent compared to long-chain PFAS. Kinetic studies showed that less hydrophobic PFAS (perfluorobutanoic acid (PFBA)-perfluorohexanoic acid (PFHxA)) reached equilibrium faster and the extraction followed a pseudo-second order model with r2 values up to 0.9874. The applicability of the PIL-thin film microextraction (TFME) device for quantitative analysis was demonstrated by a calibration curve in a concentration range from 1 ng L-1 to 2500 ng L-1, which showed good accuracy (70-130%), precision (<20%), and limits of quantification from 1 ng L-1 to 50 ng L-1.

Effective preconcentration of volatile per- and polyfluoroalkyl substances from gas and aqueous phase via solid phase microextraction

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are synthetic fluorinated chemicals of increasing global concern due to their persistence, toxicity, and widespread presence in the environment. Neutral and volatile PFAS, used in firefighting foams and non-stick coatings, are precursors of perfluorinated acids such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) and necessitate effective preconcentration methods for isolation from aqueous and gaseous phases.

RESULTS

In this work, a robust quantitative method was rigorously optimized and validated to achieve effective preconcentration and quantification of neutral volatile PFAS, including fluorotelomer alcohols (FTOHs), perfluorooctanesulfonamides (FOSAs), and a perfluorooctanesulfonamido-ethanol (FOSE). Leveraging the versatility of solid phase microextraction (SPME) for sampling in different extraction modes, volatile PFAS were pre-concentrated in gaseous (Headspace-SPME) and aqueous (Direct Immersion-SPME) phases. The impact of temperature, time, and aqueous media composition on extraction efficiency was assessed, with analysis performed using gas chromatography-mass spectrometry. LOQs between 0.005 μg L-1 and 5 μg L-1 were achieved for direct immersion-SPME and 0.005 μg L-1 to 0.25 μg L-1 for headspace-SPME, also demonstrating excellent repeatability with relative standard deviations (RSD%) below 11 %.

SIGNIFICANCE

This work highlights the need for efficient pre-chromatographic separation methods for extraction and preconcentration of volatile PFAS. The developed Headspace and Direct Immersion-SPME methods provide a practical, solvent-free, automated solution for extraction and preconcentration of volatile PFAS from aqueous and gaseous samples. These methods enrich the analytical toolbox for PFAS analysis and can be applied to understanding how PFAS enter the environment and partition in heterogeneous systems.

Challenges in PFAS Postdegradation Analysis: Insights from the PFAS-CTAB Model System

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used for their oil and water-repellent properties. Their environmental persistence and potential health risks have raised significant concerns. As PFAS degrades through remediation or natural processes, they form complex mixtures of the original chemicals, transformation byproducts, and degradation additives. Analyzing PFAS after degradation presents analytical challenges due to possible chemical and physical interactions, including ion pairing, micelle formation, and complexation. These factors can significantly impact the precision and accuracy of PFAS measurements, yet they are often overlooked in PFAS degradation studies. In this work, we demonstrate that with the addition of ppb-level cetyltrimethylammonium bromide (CTAB), a cationic surfactant used in PFAS plasma-based degradation, the PFAS calibration curve linearity, sensitivity, and reproducibility are severely compromised. Isotopically labeled internal standards cannot fully correct these issues. Furthermore, the standard EPA methods 537.1, 533, and 1633 could not accurately recover PFAS concentrations in the PFAS and CTAB mixtures, with severe matrix effects observed for longer-chain and nitrogen-containing PFAS. Among these methods, Method 1633 is currently the most suitable option for postdegradation analysis. Method 1633 showed the lowest CTAB interference because this method used another weak ion pair additive, formic acid or acetic acid (in commercial lab analysis), to acidify the sample before LC-MS/MS analysis and added an isotopically labeled internal standard. For future PFAS degradation studies, we recommend systematically evaluating the matrix effect on the PFAS quantification using a recovery matrix to validate the analytical methods before use.

Remote sampling of persistent organic pollutants by a home-made thin film device

Fast and accurate determination of persistent organic pollutants (POPs) plays a crucial role in addressing concerns related to public security and environmental safety. Herein, a unique thin film based solid phase microextraction (denoted as TF-SPME) method was reported and used for on-site analysis of POPs via loading the TFs into a homemade sampling device and equipped on a drone, which can load up to 6 pieces of TFs at the same time. The parallel 6 pieces of TFs offered significant advantages in terms of efficiency, accuracy, cost-effectiveness and comparability of sampling. The detection limit for polychlorinated biphenyls and polyaromatic hydrocarbons was as low as 0.03 ng L-1, far below the regulatory thresholds for drinking water prescribed by the United States Environmental Protection Agency. The standard deviations were ranged between 2.7 % and 9.9 %, showcasing its remarkable precision on POPs analysis. Then, by facilely equipping TF-SPME on a drone, remotely controlled sampling and on-site analysis in real water samples was realized. The concentrations were determined to be from 0.12 ng L-1 to 1.01 ng L-1 for PCBs and 0.53 ng L-1 to 19.93 ng L-1 for PAHs in the river water of Guangzhou downtown area. This study demonstrates the possibility of practical monitoring POPs with constructing novel sampling device and hopefully expands the toolbox for remote analysis of potential chemotoxicity and biotoxicity samples.

Latest trends in the environmental analysis of PFAS including nontarget analysis and EOF-, AOF-, and TOP-based methodologies

Ubiquitous environmental occurrence of per- and polyfluoroalkyl substances (PFAS) underscores the critical need to broaden investigative efforts in effective screening, risk assessment, and remediation. Owing to the broad spectrum of PFAS, various analytical techniques have been extensively utilized to attain inclusivity, with notable attention given to methods such as extractable organic fluorine (EOF), adsorbable organic fluorine (AOF), and the total oxidizable precursor (TOP) assay. These techniques expand the scope of PFAS analysis by estimating perfluoroalkyl acid precursors or the total organochlorine fraction. This review offers a comprehensive comparative overview of up-to-date methodologies, alongside acknowledging the inherent limitations associated with their applications. When coupled with target analysis via low-resolution tandem mass spectrometry, these techniques offer a potential estimation of total PFAS concentrations. Yet, analytical challenges such as the limited availability of reference analytical standards, partial PFAS adsorption, and the entrapment of fluorinated inorganic anions on adsorbent materials often restrict the comprehensiveness of PFAS analysis. So, integrating nontarget analysis using high-resolution mass spectrometry (HRMS) tools fortifies these PFAS mass balance approaches, enabling the development of a more holistic approach for an environmental analysis framework. This review provides additional insights into the comparative advantages of PFAS analytical approaches and explores various data prioritization strategies in nontarget screening methods. It advocates for the necessary optimization of PFAS extraction methods, asserting that integrating the nontarget approach would foster the establishment of a comprehensive monitoring framework across diverse environmental matrices. Such integration holds promise for enhancing scientific comprehension of PFAS contamination across diverse environmental matrices.

The role of Drp1 - Pink1 - Parkin - mediated mitophagy in perfluorobutane sulfonate- induced hepatocyte damage

Perfluorobutane sulfonate (PFBS) is recognized as a highly persistent environmental contaminant, notorious for its chemical stability and enduring presence in ecosystems. Its propensity for persistence and environmental mobility allows PFBS to infiltrate the human body, predominantly accumulating in the liver where it poses a potential risk for hepatic damage. This investigation aimed to explore the outcomes of PFBS on the physiological functionalities of hepatocytes in vitro. To this end, hepatocytes were exposed to 750 ug/ml PFBS, followed by an analysis of various cellular phenotypes and functionalities, including assessments of cell viability and mitochondrial integrity. The findings indicated that PFBS exposure led to a suppression of cell proliferation and an increase in apoptotic cell death. Moreover, PFBS exposure was found to augment the generation of reactive oxygen species (ROS) and induce significant mitochondrial dysfunction. Gene expression analysis identified significant changes in genes associated with numerous tumor signaling pathways and autophagy signaling pathways. Further examinations revealed an increase in cellular mitophagy following PFBS exposure, coupled with the activation of the mitophagy-associated Drp1/Pink1/Parkin pathway. Inhibition of mitophagy was observed to concurrently amplify cellular damage and inhibit the Drp1/Pink1/Parkin pathway. Together, these findings highlight PFBS's capacity to inflict hepatocyte injury through mitochondrial disruption, positioning Drp1/Pink1/Parkin-mediated mitophagy as a crucial cellular defense mechanism against PFBS-induced toxicity.

Characterization of a mixed mode fluorocarbon/weak anion exchange sorbent for the separation of perfluoroalkyl substances

The ubiquitous presence and persistence of per- and polyfluoroalkyl substances (PFAS) in the environment have raised concerns in the scientific community. Current research efforts are prioritizing effective PFAS remediation through novel sorbents with orthogonal interaction mechanisms. Recognized sorption mechanisms between PFAS and sorbents include hydrophobic, electrostatic, and fluorine-fluorine interaction. The interplay of these mechanisms contributes significantly to improved sorption capacity and selectivity in PFAS separations. In this study, a primary/secondary amine-functionalized polystyrene-divinylbenzene (Sepra-WAX) polymer was modified to create a fluorinated WAX resin (Sepra-WAX-KelF-PEI). The synthesis intermediate (Sepra-WAX-KelF) was also tested to assess the improvement of the final product (Sepra-WAX-KelF-PEI). The adsorption capacity of Sepra-WAX, Sepra-WAX-KelF, and Sepra-WAX-KelF-PEI, and their interactions with PFAS were evaluated. The effect of pH, ionic strength, and organic solvents on PFAS sorption in aqueous solution was also investigated. The sorbents showed varied adsorption capacities for perfluorooctanoic acid, perfluoropentanoic acid, perfluoro-n-decanoic acid, and hexafluoropropylene oxide dimer acid, with the average extraction capacity of the four analytes being Sepra-WAX-KelF-PEI (523 mg/g) > Sepra-WAX (353 mg/g) > Sepra-WAX-KelF (220 mg/g). Sepra-WAX-KelF-PEI provided the highest adsorption capacity for all analytes tested, proving that the combination of electrostatic and hydrophobic/fluorophilic interactions is crucial for the effective preconcentration of PFAS and its future applications for PFAS remediation from aqueous solutions.

Embedding Mixed Sorbents in Binder: Solid-Phase Microextraction Coating with Wide Extraction Coverage and Its Application in Environmental Water Analysis

Solid-phase microextraction (SPME) is a simple and highly effective sample-preparation technique for water analysis. However, the extraction coverage of a given SPME device with a specific coating can be an issue when analyzing multiple environmental contaminants. Therefore, instead of synthesizing one sorbent material with dual or multiple functions, we investigated a new strategy of preparing SPME blades using a homogeneous slurry made by mixing three different sorbent particles─namely, hydrophobic/lipophilic balanced (HLB), HLB-weak cationic exchange (HLB-WCX), and HLB-weak anionic exchange (HLB-WAX)─with a polyacrylonitrile (PAN) binder. The developed coating is matrix compatible, as the binder functions not only as a glue for immobilizing the sorbent particles but also as a porous filter, which only allows small molecules to enter the pores and interact with the particles, thus avoiding contamination from large elements. The results confirmed that the proposed mixed-coating SPME device provides good extraction performance for polar and nonpolar as well as positively and negatively charged compounds. Based on this device, three comprehensive analytical methodologies─high-throughput SPME-LC-MS/MS (for the quantitative analysis of targeted drugs of abuse and artificial sweeteners), in-bottle SPME-LC-high resolution MS (HRMS) (for the untargeted screening of organic contaminants), and on-site drone sampling SPME-LC-HRMS (for on-site sampling and untargeted screening)─were developed for use in environmental water analysis. The resultant data confirm that the proposed strategies enable comprehensive water quality assessment by using a single SPME device.

Matrix effects demystified: Strategies for resolving challenges in analytical separations of complex samples

Matrix effects can significantly impede the accuracy, sensitivity, and reliability of separation techniques presenting a formidable challenge to the analytical process. It is crucial to address matrix effects to achieve accurate and precise measurements in complex matrices. The multifaceted nature of matrix effects which can be influenced by factors such as target analyte, sample preparation protocol, composition, and choice of instrument necessitates a pragmatic approach when analyzing complex matrices. This review aims to highlight common challenges associated with matrix effects throughout the entire analytical process with emphasis on gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and sample preparation techniques. These techniques are susceptible to matrix effects that could lead to ion suppression/enhancement or impact the analyte signal at various stages of the analytical workflow. The assessment, quantification, and mitigation of matrix effects are necessary in developing any analytical method. Strategies can be implemented to reduce or eliminate the matrix effect by changing the type of ionization, improving extraction and clean-up methods, optimization of chromatography conditions, and corrective calibration methods. While development of an effective strategy to completely mitigate matrix effects remains elusive, an integrated approach that combines sample preparation, analytical extraction, and effective instrumental analysis remains the most promising avenue for identifying and resolving matrix effects.

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.

Impact of per- and polyfluorinated alkyl substances (PFAS) on the marine environment: Raising awareness, challenges, legislation, and mitigation approaches under the One Health concept

Per- and polyfluorinated alkyl substances (PFAS) have long been known for their detrimental effects on the ecosystems and living organisms; however the long-term impact on the marine environment is still insufficiently recognized. Based on PFAS persistence and bioaccumulation in the complex marine food network, adverse effects will be exacerbated by global processes such as climate change and synergies with other pollutants, like microplastics. The range of fluorochemicals currently included in the PFAS umbrella has significantly expanded due to the updated OECD definition, raising new concerns about their poorly understood dynamics and negative effects on the ocean wildlife and human health. Mitigation challenges and approaches, including biodegradation and currently studied materials for PFAS environmental removal are proposed here, highlighting the importance of ongoing monitoring and bridging research gaps. The PFAS EU regulations, good practices and legal frameworks are discussed, with emphasis on recommendations for improving marine ecosystem management.