Sensitive and accurate analysis of poly and perfluoroalkyl substances (PFASs) using both targeted and non-targeted approaches for assessment of legacy and unknown compounds
Abstract
Environmental poly- and perfluoroalkyl substance (PFAS) contamination is a major problem at hundreds of DoD sites with historical use of aqueous film forming foam (AFFF) as well as use at airports. Interest in PFASs has increased across public, regulatory, commercial, and academic sectors as there is a growing body of evidence that PFASs are a human and ecosystem health risk. There already exists growing evidence that some PFAS compounds bioaccumulate. However, the extent and mechanisms of bioaccumulation and biomagnification of PFASs in food webs, as well as their bioavailability (i.e., the ability to interact with biota in a given environment) are not well characterized nor understood. Perfluoroalkyl acids (PFAAs), which have a negatively charged head group, low volatility, and high water solubility, are considered to be highly mobile in aqueous phase, and PFAA transport has often been observed or inferred in the environment. As a consequence of such mobility and concerns of their human health effects, drinking water wells at several downstream localities of DoD sites have been temporarily abandoned. The cost to remediate PFASs at military sites is estimated to be $2 billion. PFASs family includes a broad range of compounds that can be categorized by polar head group, chain length, charge (anionic, cationic, or zwitterionic), and extent of fluorination; the intrinsic physicochemical properties influence their fate, transport, and degradability. Quantitation relies on availability of standards (native and mass labeled), and is possible for tens of compounds across a range of PFAS classes. However, hundreds of PFASs compounds have been identified using high resolution mass spectrometry using a liquid chromatography quadrupole time-of-flight mass spectrometry (LC QTOF/MS). Several tools will be used for identification of potential unknown PFASs: 1) accurate mass for determination of molecular formula (resolution 20,000; sub 2-ppm mass accuracy); 2) comparison of control and treatment samples to identify production of new compounds (e.g., pre- and post- degradation experiment); 3) mass defect filtering to highlight molecules with the negative mass defect that is characteristic of PFASs (due to the inclusion of multiple fluorine atoms, which have an accurate mass of 18.9984 amu which is less than the nominal mass); 4) Kendrick mass defect plots, which produce lines based on homologous series (i.e., differences in number of CF2 groups). This proposal will support the purchase of components of a Sciex X500R LC-QTOF/MS system, which will be setup for optimized PFASs quantification and non-target analysis. The X500R system achieves accurate and sensitive quantification of PFASs (e.g., where analytical standards are available), and also allows non-target analysis through the proprietary MSn and SWATH approaches. Sciex has a very strong team that has been working of PFASs target and non-target analysis for greater than five-years, and has collaboratively been developing a library of PFASs that includes more than 300 analytes. The LC-QTOF/MS system would support three DoD funded projects that address PFAS fate, transport, biouptake, and treatment, as well as future PFASs analysis in support of the DoDs efforts to understand and mitigate risk from PFASs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 01, 2019
- Source ID
- W911NF1910131
Entities
People
- Erica R McKenzie
Organizations
- Army Contracting Command
- Temple University
- United States Army