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Improving Selection of Standards for Semi-quantitation of Perfluoroalkyl Substances (PFASs)
Citation:
Miller, K., N. Yeung, J. McCord, L. Groff, AND M. Strynar. Improving Selection of Standards for Semi-quantitation of Perfluoroalkyl Substances (PFASs). 2021 Nontarget Analysis for Environmental Risk Assessment, Durham, NC, May 23 - 27, 2021.
Impact/Purpose:
The SETAC Non-Targeted Analysis (NTA) focus topic meeting is a meeting of the world's leading experts on the use of high resolution mass spectrometry (HRMS) and NTA applications. This poster will discuss methodology of choosing the best PFAS standards for improving semi-quantitation of this class of chemicals. This work will help other NTA researchers and modelers who want to better estimate the concentration of PFAS in their samples.
Description:
Per- and polyfluoroalkyl substances (PFASs) are emerging contaminants widely used in a variety of industrial and consumer applications (e.g., fire-fighting foams, cosmetics, food wrappers, household products, etc.). These man-made chemicals persist ubiquitously in various environmental media due to their inability to biodegrade. It’s estimated that thousands of PFASs are manufactured either purposefully or as byproducts, yet many of these chemicals remain unknown and are not registered in the Toxic Substances Control Act (TSCA) Chemical Substance Inventory. Characterizing these unknown compounds is important for understanding our exposure and the toxicological effects, and non-targeted analysis (NTA) and high resolution mass spectrometry (HRMS) have furthered the discovery of novel PFASs. However, the lack of authentic standards prevents quantitation of these unknowns. Instead semi-quantitation must be used to estimate concentration, but there is no published guidance about choosing the best PFAS standards for semi-quantifying novel compounds. This study focuses on improving semi-quantitation of PFASs through the modeling of PFAS standards’ calibration curves based on chemical similarity. PFASs standards from different classes (e.g., perfluoroether carboxylic acids (PFECAs), perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkanesulfonic acids (PFSAs), etc.) were analyzed on a Thermo Vanquish coupled to a Thermo Orbitrap Fusion. US EPA’s CompTox Chemicals Dashboard analyzed these standards’ structures using ChemoTyper to create chemical fingerprints, and Tanimoto Coefficients were calculated to compare chemical similarity across the set of observed chemicals. Global calibration curves were generated via linear regression of the signal intensities of all standards, as well as local calibration curves based on the five nearest neighbors. Proof-of-concept and accuracy of prediction were shown by treating some standards as unknowns and comparing their standard calibration curve to a model local calibration curve. Improving the way PFASs standards are chosen for semi-quantitation will help NTA researchers and modelers better estimate concentrations of unknown PFASs.