Analysis of per-and polyfluorinated alkyl substances by chromatography-mass spectrometry: A review.

Per- and polyfluoroalkyl substances (PFAS) have garnered increasing attention in recent years and non-targeted analysis (NTA) has become essential for elucidating novel PFAS structures. NTA and PFAS research have been dominated by liquid chromatography - mass spectrometry (LC-MS) with gas chromatography - mass spectrometry (GC-MS) used less often as evidenced by bibliometrics. However, the performance of GC-MS in NTA studies (GC-NTA) rivals that of LC-ESI-MS and GC-MS is shown to cover a complimentary chemical space. An LC-ESI-MS amenability model applied to a list of approximately 12,000 PFAS revealed that less than 10% of known PFAS chemistry is predicted to be amenable to typical LC-MS analysis. Therefore, there is strong potential for applying GC-MS methods to more fully assess the PFAS environmental contamination landscape, uniquely shedding light on both known and novel PFAS, especially within the chemical space realm of volatile and semi-volatile PFAS. Waste streams from fluorochemical manufacturing facilities have been heavily studied using LC-MS and targeted GC-MS; however, GC-NTA is needed to discover novel PFAS that are not amenable to LC-MS emitted from facilities. Studies on the incineration of PFAS-containing materials, such as aqueous film forming foam, have focused on the destruction of parent compounds and little is known about the transformation products formed during such processes. GC-NTA holds the potential to elucidate transformation products formed when PFAS are incinerated. Wastewater treatment plants and landfills are known sources of PFAS to the environment, yet GC-NTA is needed to understand air emissions of PFAS and PFAS transformation products from these sources. Consumer products are known to lead to indoor exposures to PFAS via emissions to air and dust but research in this area has either used LC-MS or targeted GC-MS. Despite the challenges with advancing GC-NTA, we call on NTA researchers, grantors, managers, and other stakeholders to recognize the potential and necessity of GC-NTA in PFAS research so that we may face these challenges together.

Per- and polyfluoroalkyl substances (PFAS) is an emerging class of organic pollutants of concern and is now prevalent in environmental matrices including water, soil, air, and biological. So far, several standard analytical methods have been developed to systematically analyze PFAS in different environmental matrices. However, the complexity of environmental matrices makes the effective extraction of PFAS difficult, and the legacy PFAS is gradually changing into a new PFAS with short chain and unknown structure in production, which makes the analysis of PFAS challenging. In this review, the following aspects are summarized: (1) the advances in standard analytical methods for PFAS in different environmental matrices, and further generalizes the updating novel extraction and detection methods; (2) the analysis of unknown PFAS, the suspect and non-targeted screening analysis method of PFAS based on high-resolution mass spectrometry (HRMS) is systematically described.

Chapter 14 - Analysis of GenX and Other Per- and Polyfluoroalkyl Substances in Environmental Water Samples

Sixty leading members of the scientific, engineering, regulatory, and legal communities assembled for the PFAS Experts Symposium in Arlington, Virginia on May 20 and 21, 2019 to discuss issues related to per‐ and polyfluoroalkyl substances (PFAS) based on the quickly evolving developments of PFAS regulations, chemistry and analytics, transport and fate concepts, toxicology, and remediation technologies. The Symposium created a venue for experts with various specialized skills to provide opinions and trade perspectives on existing and new approaches to PFAS assessment and remediation in light of lessons learned managing other contaminants encountered over the past four decades. The following summarizes several consensus points developed as an outcome of the Symposium: Regulatory and policy issues: The response by many states and the US Environmental Protection Agency (USEPA) to media exposure and public pressure related to PFAS contamination is to relatively quickly initiate programs to regulate PFAS sites. This includes the USEPA establishing relatively low lifetime health advisory levels for PFAS in drinking water and even more stringent guidance and standards in several states. In addition, if PFAS are designated as hazardous substances at the federal level, as proposed by several Congressional bills, there could be wide‐reaching effects including listing of new Superfund sites solely for PFAS, application of stringent state standards, additional characterization and remediation at existing sites, reopening of closed sites, and cost renegotiation among PRPs. Chemistry and analytics: PFAS analysis is confounded by the lack of regulatory‐approved methods for most PFAS in water and all PFAS in solid media and air, interference with current water‐based analytical methods if samples contain high levels of suspended solids, and sample collection and analytical interference due to the presence of PFAS in common consumer products, sampling equipment, and laboratory materials. Toxicology and risk: Uncertainties remain related to human health and ecological effects for most PFAS; however, regulatory standards and guidance are being established incorporating safety factors that result in part per trillion (ppt) cleanup objectives. Given the thousands of PFAS that may be present in the environment, a more appropriate paradigm may be to develop toxicity criteria for groups of PFAS rather than individual PFAS. Transport and fate: The recalcitrance of many perfluoroalkyl compounds and the capability of some fluorotelomers to transform into perfluoroalkyl compounds complicate conceptual site models at many PFAS sites, particularly those involving complex mixtures, such as firefighting foams. Research is warranted to better understand the physicochemical properties and corresponding transport and fate of most PFAS, of branched and linear isomers of the same compounds, and of the interactions of PFAS with other co‐contaminants such as nonaqueous phase liquids. Many PFAS exhibit complex transport mechanisms, particularly at the air/water interface, and it is uncertain whether traditional transport principles apply to the ppt levels important to PFAS projects. Existing analytical methods are sufficient when combined with the many advances in site characterization techniques to move rapidly forward at selected sites to develop and test process‐based conceptual site models. Existing remediation technologies and research: Current technologies largely focus on separation (sorption, ion exchange, or sequestration). Due to diversity in PFAS properties, effective treatment will likely require treatment trains. Monitored natural attenuation will not likely involve destructive reactions, but be driven by processes such as matrix diffusion, sorption, dispersion, and dilution. The consensus message from the Symposium participants is that PFAS present far more complex challenges to the environmental community than prior contaminants. This is because, in contrast to chlorinated solvents, PFAS are severely complicated by their mobility, persistence, toxicological uncertainties, and technical obstacles to remediation—all under the backdrop of stringent regulatory and policy developments that vary by state and will be further driven by USEPA. Concern was expressed about the time, expense, and complexity required to remediate PFAS sites and whether the challenges of PFAS warrant alternative approaches to site cleanups, including the notion that adaptive management and technical impracticability waivers may be warranted at sites with expansive PFAS plumes. A paradigm shift towards receptor protection rather than broad scale groundwater/aquifer remediation may be appropriate.

Per- and polyfluoroalkyl substances (PFASs) are a group of anthropogenic chemicals widely used in manufacture and daily necessities, which are contaminants ubiquitous existed in various environmental matrices and biota. Due to the persistent, bioaccumulative, long-range transport and potential toxic behaviors, production of perfluorooctane sulfonic acid was voluntarily phased out. Perfluorooctanoic acid, its salt and related compounds were also proposed to be included the Stockholm Convention. Restrictions on production and usage of PFAS chemicals have resulted in emergence of novel PFAS compounds through direct manufacturing emissions and indirect transformation pathways, and increasing attention has been focused on these alternatives. In this review, we summarized recent investigations on major groups of emerging PFASs with various molecular structures, and current analytical strategies on the identification of unknown organic fluoride components were overviewed. Four classes of emerging PFASs are covered, including short-chain perfluoroalkyl substances, cyclic perfluoroalkyl acids, perfluoropolyethers and chlorine or hydrogen-substituted polyfluoroalkyl substances. Current knowledge on molecular structures, production and application, environmental behaviors and potential biological effects are summarized, if available. Known PFASs were noticed as a small part of organic fluorinated compounds in the environment. Consequently, new analytical strategies, such as the mass balance analysis and the oxidative conversion methods, were developed for the analysis of unknown fluorinated components. Mass balance analysis of extractable organic fluorine were used to predict the content of unknown organic fluorine in various environmental matrices including sea water, soil, and human blood. Extractable organic fluorine could be exactly quantified after conversion into inorganic fluoride by high-temperature combustion, and known fluorinated components could also be measured by liquid chromatography tandem mass spectrometry. The difference in contents between extractable organic fluorine and known fluorinated components was thus considered as components of unknown organic fluorine. The oxidative conversion method was especially superior for the analysis of fluorinated precursors such as fluorotelomer sulfonates, perfluoroalkane sulfonamides and fluorotelomer phosphate diesters, in which these poly- fluoroalkyl substances could be transformed into known perfluoroalkyl carboxylates (PFCAs) by reaction with hydroxyl radicals at basic conditions. The content of polyfluoroalkyl precursors could be determined by comparing the change of PFCAs contents before and after the oxidation assay. Compared with the mass balance analysis method, this oxidative conversion method require quantification of more PFAS terminal products, and it was not applicable for stable perfluorinated compounds. Meanwhile, occurrence of a variety of novel PFAS analogues have brought challenges on PFAS analysis. For instance, varied molecular structures of emerging PFASs result in distinct physical-chemical properties, which further complicate the analytical process including sample pretreatment and chromatographic isolation. Development of additional methods, such as hydrophilic interaction chromatography (HILIC) for the analysis of short chain PFASs and orthogonal liquid chromatography for the analysis of zwitterionic, cationic, and anionic fluorinated chemicals, are urgently needed. Statistical tools including mass spectrum deconvolution, peak picking, alignment and feature filtering would be promising for confirmation of novel PFAS molecular structures. Also, environmental transformation of PFAS precursors are still ambiguous. Application of strategies in metabolomics analysis might facilitate studies on degradation mechanism of PFAS chemicals.

Currently, the availability of multilaboratory‐validated analytical methods for per‐ and polyfluoroalkyl substances (PFAS) is limited. Two of the more commonly known methods are the finalized United States Environmental Protection Agency (EPA) methods for the analysis of select PFAS in drinking water samples, EPA 537.1, Determination of Selected Per‐ and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) (EPA 600‐R‐20‐006) and EPA 533, Determination of Per‐ And Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry (EPA 815‐B‐19‐020) These two methods were developed specifically for drinking water samples, which generally do not have matrix interferences and are generally an easier matrix to analyze. EPA also finalized SW‐846 Method 8327, Per‐ and Polyfluoroalkyl Substances (PFAS) by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS), which covers the analysis of select PFAS in nonpotable water matrices. However, one of the critical deficiencies in this method is the lack of the gold standard for quantitation, isotope dilution, which has become a critical necessity for the analysis of PFAS in nondrinking water matrices to accommodate for potential matrix interferences. In addition, the United States Department of Defense (DoD) Environmental Data Quality Workgroup (EDQW) has stated that SW‐846 Method 8327 should only be used as a screening method and should not be used for the collection of definitive data. The release of Draft EPA Method 1633, Analysis of Per‐and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC‐MS/MS (EPA 821‐D‐21‐001), for nonpotable water matrices, is a first step toward providing the laboratory community with a standardized method that can provide accurate results for PFAS in nonpotable water matrices.

As quickly as our understanding of the nature and extent of per‐ and polyfluoroalkyl substances (PFAS) in the environment has developed, the analytical chemistry tools we use to study and quantify them have evolved. The last 5 years have seen commercial laboratories scramble to analyze atypical and unusual samples submitted by concerned citizens and governmental agencies. The unusual matrices have pushed innovative sample extraction techniques, as the regulated community and the laboratories await a final multilaboratory validated method to provide direction for the analysis of PFAS in matrices beyond drinking water. The large number of PFAS compounds has also sparked interest in the development of methods to screen for all PFAS without quantifying the individual constituents. Measurement of total PFAS is also useful in consumer product testing. New methods to determine total PFAS are in varying stages of development and are described in detail herein. The fact that there are more PFAS chemicals than can be quantified by commercial laboratories has also promoted the development of nontarget analysis (NTA) using sophisticated instrumentation. This article provides the basis of NTA and examples of its novel applications in forensics and compound identification. The pace of change in PFAS analysis is breathtaking and challenging for all those studying environmental impacts of PFAS. Updates on key topics as can be found in this article serve an important need for the remediation community.

Per- and polyfluoroalkyl substances (PFAS) are a diverse group of synthetic chemicals that have gathered significant attention because of their persistence in the environment and potential health risks. Analytical methods for PFAS detection and quantification have been developed to address the complex nature of these compounds in various matrices such as water, soil, air, and biological samples. This review provides a brief yet comprehensive overview of the separation science methods utilized for PFAS analysis, including liquid chromatography (LC), gas chromatography (GC), ion chromatography (IC), capillary electrophoresis (CE), and supercritical fluid chromatography (SFC). Additionally, mass spectrometry (MS) detection techniques, sample preparation methodologies such as solid-phase extraction (SPE) and solid-phase microextraction (SPME) are discussed. Special emphasis is placed on the analytical challenges posed by the diversity of PFAS compounds and their occurrence in different environmental and biological contexts. This review aims to provide a summary of the most current analytical techniques and their applications in PFAS research, contributing to the ongoing efforts to monitor and mitigate PFAS contamination.

Novel perfluoroalkyl substances (PFAS) discovered in whole blood using automated non-targeted analysis of dried blood spots

Rapid detection of per- and polyfluoroalkyl substances (PFAS) using paper spray-based mass spectrometry

A sensitive analytical method has been developed and validated for the determination of 16 polyfluorinated alkyl substances (PFAS) in fine airborne particulate matter (PM2.5) using on-line solid phase extraction (SPE) coupled with liquid chromatography (LC) – negative electrospray ionisation high resolution mass spectrometry (−) ESI-HRMS. On-line SPE allows simultaneous sample clean-up from interfering matrices and lower limits of detection (LODs) by injecting a large volume of sample into the LC system without compromising chromatographic efficiency and resolution. The method provides LODs in the range 0.08–0.5 pg/mL of sample extract allowing detection of selected PFAS in aerosol particles at low fg/m3 level and showed good tolerance to the considered PM matrix. The validated method was applied for analysis of PFAS in ambient PM2.5 samples collected at two urban locations in Ireland, i.e., Enniscorthy and Dublin. Several PFAS were observed above the detection limit, including perfluorobutyrate (PFBA), perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (L-PFBS) and perfluorononanoic acid (PFNA), as well as fluorotelomer sulfonates: 4:2 FTS, 6:2 FTS and 8:2 FTS. The results indicate that some toxic PFAS, such as PFOS and PFOA, are still detected in the environment despite being phased out from production and subject to restricted use in the EU and USA for more than two decades. Observation of fluorotelomer sulfonates (4:2 FTS, 6:2 FTS and 8:2 FTS, which are used as alternatives for legacy PFOA and PFOS) in ambient PM2.5 samples raises a concern about their persistence in the atmosphere and impact on human health considering emerging evidence that they could have similar health endpoints as PFOA and PFOS. To our knowledge, this is the first study to identify PFAS in ambient PM2.5 at urban locations in Ireland and also the first study to detect 4:2 and 8:2 fluorotelomer sulfonates in atmospheric aerosol particles.

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of man-made chemicals that are persistent and highly stable in the environment. Fish consumption has been identified as a key route of PFAS exposure for humans. However, routine fish monitoring targets only a handful of PFAS, and non-targeted analyses have largely only evaluated fish from heavily PFAS-impacted waters. Here, we evaluated PFAS in fish fillets from recreational and drinking water sources in central North Carolina to assess whether PFAS are present in these fillets that would not be detected by conventional targeted methods. We used liquid chromatography, ion mobility spectrometry, and mass spectrometry (LC-IMS-MS) to collect full scan feature data, performed suspect screening using an in-house library of 100 PFAS for high confidence feature identification, searched for additional PFAS features using non-targeted data analyses, and quantified perfluorooctanesulfonic acid (PFOS) in the fillet samples. A total of 36 PFAS were detected in the fish fillets, including 19 that would not be detected using common targeted methods, with a minimum of 6 and a maximum of 22 in individual fish. Median fillet PFOS levels were concerningly high at 11.6 to 42.3 ppb, and no significant correlation between PFOS levels and number of PFAS per fish was observed. Future PFAS monitoring in this region should target more of these 36 PFAS, and other regions not considered heavily PFAS contaminated should consider incorporating non-targeted analyses into ongoing fish monitoring studies.

There is a lack of agreement on a suitable container material for per- and polyfluoroalkyl substances (PFAS) analysis, particularly at trace levels. In this study, the losses of 18 short- and long-chain (C4–C10) PFAS to commonly used labware materials (high-density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), polypropylene co-polymer (PPCO), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and glass were investigated. The influence of sample storage and preparation conditions, i.e., storage time, solvent composition, storage temperatures (4 °C and 20 °C), and sample agitation techniques (shaking and centrifugation) on PFAS losses to the container materials were investigated. The results showed higher losses for most of the considered PFAS (up to 50.9%) in 100% aqueous solutions after storage for 7 days regardless of the storage temperature compared to those after 3 days. Overall, the order of losses to different materials varied for individual PFAS, with the highest losses of long-chain PFAS observed to PP and HDPE after 7-day storage at room temperature. The addition of methanol to aqueous PFAS solutions reduced the losses of long-chain PFAS to all tested materials. The use of sample centrifugation and shaking did not influence the extent of losses for most of the PFAS in 80:20 water:methanol (%, v/v) to container materials except for 8:2 fluorotelomer sulfonic acid (8:2 FTS), 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS), perfluorodecanoic acid (PFDA) and 4:2 fluorotelomer sulfonic acid (4:2 FTS). This study demonstrates lower losses of both long- and short-chain PFAS to glass and PET. It also highlights the need for caution when deciding on sample preparatory steps and storage during the analysis of PFAS.

Incorporating ultrashort-chain compounds into the comprehensive analysis of per- and polyfluorinated substances in potable and non-potable waters by LC-MS/MS

Software Comparison for Nontargeted Analysis of PFAS in AFFF-Contaminated Soil.