Non-Targeted PFAS Suspect Screening and Quantification of Drinking Water Samples Collected through Community Engaged Research in North Carolina's Cape Fear River Basin.

A community engaged research (CER) approach was used to provide an exposure assessment of poly- and perfluorinated (PFAS) compounds in North Carolina residential drinking water. Working in concert with community partners, who acted as liaisons to local residents, samples were collected by North Carolina residents from three different locations along the Cape Fear River basin: upper, middle, and lower areas of the river. Residents collected either drinking water samples from their homes or recreational water samples from near their residence that were then submitted by the community partners for PFAS analysis. All samples were processed using weak anion exchange (WAX) solid phase extraction and analyzed using a non-targeted suspect screening approach as well as a quantitative approach that included a panel of 45 PFAS analytes, several of which are specific to chemical industries near the collection site locations. The non-targeted approach, which utilized a suspect screening list (obtained from EPA CompTox database) identified several PFAS compounds at a level two confidence rating (Schymanski scale); compounds identified included a fluorinated insecticide, a fluorinated herbicide, a PFAS used in polymer chemistry, and another that is used in battery production. Notably, at several locations, PFOA (39.8 ng/L) and PFOS (205.3 ng/L) were at levels that exceeded the mandatory EPA maximum contaminant level (MCL) of 4 ng/L. Additionally, several sites had detectable levels of PFAS that are unique to a local chemical manufacturer. These findings were communicated back to the community partners who then disseminated this information to the local residents to help empower and aid in making decisions for reducing their PFAS exposure.

Recovery of per- and polyfluoroalkyl substances after solvent evaporation.

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative chemicals that can be toxic at very low levels. Many of these compounds have unusual chemical properties that can have a large impact on analytical methods intended to quantitate them. When analyzing environmental samples, concentrating extraction eluents can greatly increase the sensitivity of PFAS extraction and analysis workflows. However, data on PFAS stability when evaporated under vacuum drying conditions are lacking. In this study two common sample preparation methods were replicated (methanol or methanolic ammonium hydroxide) to determine if PFAS material would undergo any observable loss during vacuum evaporation. Standards containing 49 different analytes from 7 different PFAS classes were evaporated to dryness under vacuum either with or without heat and reconstituted using one of two methods. It was found that recovery of some classes (e.g. PFSA, PFESA, FTS) was not greatly impacted by evaporation conditions or reconstitution method. Some analytes such as the very long chain PFCAs were not affected by evaporation conditions but saw drastic differences in recovery depending on the reconstitution method. Others analytes, for example PFSAms, experienced significant loss during evaporation that could not be mitigated by the chosen reconstitution method. This difference could be due to the number of fluorines present on the compound which correlated with a compound's hydrophobicity. Due to these findings, it is recommend that researchers consider PFAS class, chain length, and fluorine number when designing concentration and reconstitution protocols for PFAS to ensure conditions are optimal for the specific analytes of interest.

Development and validation of a high resolving power absolute quantitative per- and polyfluoroalkyl substances method incorporating Skyline data processing.

RATIONALE: The ability to perform absolute quantitation and non-targeted analysis on a single mass spectrometry instrument would be advantageous to many researchers studying per- and polyfluoroalkyl substances (PFAS). High-resolution accurate mass (HRAM) instrumentation (typically deployed for non-targeted work) carries several advantages over traditional triple quadrupole workflows when performing absolute quantitation. Processing this data using a vendor-neutral software would promote collaboration for these environmental studies. METHODS: LC-MS (Orbitrap Exploris 240) was used for absolute quantitation of 45 PFAS using precursor (MS1) peak areas for quantitation, whereas isotope pattern matching and fragmentation (MS2) pattern matching were used for qualitative identification. In addition, a fluorinated chromatographic column achieved superior separation compared to the typical C18 columns typically used in PFAS analyses. This method was validated across eight different chemical classes using recommended guidelines found in EPA Method 537.1 and Skyline data processing software. RESULTS: The validated limits of all 45 compounds, as well as metrics or accuracy and reproducibility, are reported. Most compounds achieved limits of quantitation in the range of 2-50 ng/L. Four newly released Chemours-specific compounds (PEPA, PFO3OA, PFO4DA, and PFO5DoA) were also validated. Aspects of data analysis specific to high resolving power absolute quantitation are reviewed as are the details of processing these data via Skyline. CONCLUSIONS: This method shows the feasibility of performing reproducible absolute quantitation of PFAS on an HRAM platform and does so using an open-source vendor-neutral data processing software to facilitate sharing of data across labs and institutions.

Untargeted Metabolomic Investigation of Wheat Infected with Stinking Smut Tilletia caries.

Tilletia caries infection of wheat (Triticum aestivum) has become an increasing problem in organic wheat agriculture throughout the world. Little is known about how this pathogen alters host metabolism to ensure a successful infection. We investigated how T. caries allocates resources from wheat for its growth over the life cycle of the pathogen. An untargeted metabolomics approach that combined gas chromatography time-of-flight mass spectrometry and ultraperformance liquid chromatography tandem mass spectrometry platforms was used to determine which primary or specialized metabolite pathways are targeted and altered during T. caries infection. We found that T. caries does not dramatically alter the global metabolome of wheat but instead alters key metabolites for its own nutrient uptake and to antagonize host defenses by reducing wheat's sweet immunity response and other related pathways. Our results highlight metabolic characteristics needed for selecting wheat varieties that are resistant to T. caries infection for organic agriculture. In addition, several wheat metabolites were identified that could be used in developing a diagnostic tool for early detection of T. caries infection.