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Per-and polyfluoroalkyl substances (PFAS) are a class of contaminants of emerging concern frequently used in products like aqueous firefighting foams and non-stick coatings due to their stability and surfactant-like qualities. The lack of analytical standards for many emerging PFAS have severely limited our ability to comprehensively identify unknown PFAS contaminants in the environment, especially those that occur as isomers. Annotation of small molecules and identification of unknowns based only on elemental composition and mass fragmentation patterns remain major challenges in nontarget analysis employing liquid chromatography with high-resolution mass spectrometry (LC-HRMS). In this study, chromatographic retention factors (k) and mass spectral fragmentation patterns of 32 known PFAS were determined using our optimized parameters in LC-HRMS. The same method was then used to analyze previously unidentified PFAS in actual environmental samples. Using characteristic ions observed in the MS fragmentation of PFAS, the most probable isomeric structures of the detected PFAS were predicted. To increase confidence in the predicted molecular structure, Density Functional Theory and Conductor-like Screening Model for Realistic Solvents (COSMO-RS) calculations were used to predict physicochemical properties of different constitutional isomers. The DFT calculations facilitated geometric optimization, determination of polarizability, and calculation of the chemical potential the isomers. COSMO-RS uses themore »chemical potential to predict thermodynamic properties of molecules such as pKa, solubility, and Kow. These properties were then used to make a multi-variable linear regression to predict k values. The model was trained using 32 known PFAS. The properties used were log Kow of the neutral and anion species of the PFAS, and their polarizability. The model was specific enough to predict significantly different k values of unknown compounds with similar structures, which facilitated assignment of isomeric structures of PFAS.« less

Nontarget analysis using liquid chromatography–high resolution mass spectrometry (LC–HRMS) is a valuable approach in characterizing for contaminants of emerging concern (CECs) in the environment. However, identification of these analytes can be quite costly or taxing without proper analytical standards. To circumvent this problem we utilize Quantitative structure-retention relationships (QSRR) models to predict elution order and retention times. Properties calculated from density functional theory (DFT) and the conductor-like screening model for real solvents (COSMO-RS) theory are used to produce our QSRR models, which can be calculated for virtually any analyte. We show that this methodology has been successful in identification of per- /poly-fluoroalkyl substances (PFAS) and other contaminants. Nontarget analysis using liquid chromatography– high resolution mass spectrometry (LC–HRMS) is a valuable approach in characterizing for contaminants of emerging concern (CECs) in the environment. However, identification of these analytes can be quite costly or taxing without proper analytical standards. To circumvent this problem we utilize Quantitative structureretention relationships (QSRR) models to predict elution order and retention times. Properties calculated from density functional theory (DFT) and the conductor-like screening model for real solvents (COSMO-RS) theory are used to produce our QSRR models, which can be calculated for virtually any analyte. We show thatmore »this methodology has been« less

https://doi.org/10.1021/scimeetings.0c05786

The exceptionally π-basic metal fragments {MoTp(NO)(DMAP)} and {WTp(NO)(PMe3)} (Tp = tris(pyrazolyl)borate; DMAP = 4-(N,N-dimethylamino)pyridine) form thermally stable η2-coordinated complexes with a variety of electron-deficient arenes. The tolerance of substituted arenes with fluorine-containing electron withdrawing groups (EWG; −F, −CF3, −SF5) is examined for both the molybdenum and tungsten systems. When the EWG contains a π bond (nitriles, aldehydes, ketones, ester), η2 coordination occurs predominantly on the nonaromatic functional group. However, complexation of the tungsten complex with trimethyl orthobenzoate (PhC(OMe)3) followed by hydrolysis allows access to an η2-coordinated arene with an ester substituent. In general, the tungsten system tolerates sulfur-based withdrawing groups well (e.g., PhSO2Ph, MeSO2Ph), and the integration of multiple electron-withdrawing groups on a benzene ring further enhances the π-back-bonding interaction between the metal and aromatic ligand. While the molybdenum system did not form stable η2-arene complexes with the sulfones or ortho esters, it was capable of forming rare examples of stable η2-coordinated arene complexes with a range of fluorinated benzenes (e.g., fluorobenzene, difluorobenzenes). In contrast to what has been observed for the tungsten system, these complexes formed without interference of C–H or C–F insertion.

Paleoanthropological and geological field research at Galili, Afar Regional State, Ethiopia was reinitiated in 2016. The site has been established as encompassing sediments ranging between 2.5-4.5± Ma and includes early Australopithecus and perhaps Ardipithecus. While preliminary paleoenvironmental analyses have suggested open woodland to bushland-woodland and shrubland, we present here additional evidence of the diet and functional anatomy of the Early Pliocene bovids from Galili. Fossil bovids have been recognized as a crucial tool in understanding ancient environments and serve as an important ecological indicator. Establishing the habitats of Galili is important for both understanding the environment in which the fauna, including hominins, resided and providing comparison to other contemporaneous sites. Taxonomic identification and metric analyses were performed on bovid teeth (n=93) from the 3.9-4.4 Ma Shabeley Laag and Dhidinley members to reconstruct the paleoenvironment. The sample was dominated by Reduncini, a riparian-associated tribe, and Tragelaphini, a browsing-associated tribe. Hypsodonty index was calculated for each tribe and results suggest the most abundant bovid taxa trend towards the brachydont category. Only three tribes: Alcelaphini, Antilopini, and Hippotragini fell within the mesodont category, and no tribes had hypsodont indices. Mesowear analysis of the sample indicated high occlusal relief and rounded cusp shapes weremore »most common. Taken together, our results indicate a trend in bovid diet towards mixed feeding and browsing at Galili.« less

Paleoanthropological and geological field research at Galili, Afar Regional State, Ethiopia was reinitiated in 2016. The site has been established as encompassing sediments ranging between 2.5-4.5± Ma and includes early Australopithecus and perhaps Ardipithecus. While preliminary paleoenvironmental analyses have suggested open woodland to bushland-woodland and shrubland, we present here additional evidence of the diet and functional anatomy of the Early Pliocene bovids from Galili. Fossil bovids have been recognized as a crucial tool in understanding ancient environments and serve as an important ecological indicator. Establishing the habitats of Galili is important for both understanding the environment in which the fauna, including hominins, resided and providing comparison to other contemporaneous sites. Taxonomic identification and metric analyses were performed on bovid teeth (n=93) from the 3.9-4.4 Ma Shabeley Laag and Dhidinley members to reconstruct the paleoenvironment. The sample was dominated by Reduncini, a riparian-associated tribe, and Tragelaphini, a browsing-associated tribe. Hypsodonty index was calculated for each tribe and results suggest the most abundant bovid taxa trend towards the brachydont category. Only three tribes: Alcelaphini, Antilopini, and Hippotragini fell within the mesodont category, and no tribes had hypsodont indices. Mesowear analysis of the sample indicated high occlusal relief and rounded cusp shapes weremore »most common. Taken together, our results indicate a trend in bovid diet towards mixed feeding and browsing at Galili.« less

The paleoanthropological research potential of the sediments surrounding Mt. Galili in the Afar State of Ethiopia was first established by Y. Haile-Selassie in the late 1990s. Subsequently, a team led by H. Seidler conducted a series of field campaigns through 2010. Together, these projects discovered a number of valuable fossils, including hominins, that verified the importance of the area and provided a biochronological and geochronological framework for the sediments that span the ca. 2.5 Ma to >4.5 Ma period. Field research of the Mt. Galili Formation was reinitiated by our team in 2016. We conducted a short 13-day field survey of the area with the goals of collecting additional paleontological, geological, and archeological materials to better understand the biotic context during this period and provide additional age constraints on the deposits. Much of the survey focused on sediments on the middle Pliocene-aged Shabeley Laag Member with short surveys of the older Dhidinley and Lasdanan Mbrs. Altogether, a diverse array of terrestrial non-hominin (especially monkeys, suids, proboscideans, and bovids) and hominin fauna were collected. As noted by previous workers, the sediments are dominated by fluvial and lacustrine deposits with numerous intercalated air-fall tuffs and intrusive basalts. A number of geological specimensmore »were collected and exported and await radiometric dating and tephrostratigraphic correlation analysis. Here, we will present preliminary results from the 2016 field survey. Support for the project was from NSF BCS-1519059 (SWS) and from the University of Arizona (JQ).« less