Ellington wins awards at 2023 CPRC-HDC Joint Spring Meeting

The Society of Environmental Toxicology and Chemistry 2nd Annual Hudson-Delaware & Chesapeake-Potomac Regional Chapter Joint Spring Meeting was held in Easton, Maryland from April 17 - 28, 2023. 

Authors: Marriah Ellington, Ke He, Margaret Siao, Jiabao Liang, Lee Blaney

Abstract: Per- and polyfluoroalkyl substances (PFAS) comprise more than 10,000 compounds with variable physicochemical properties. Targeted analytical approaches require standards that are limited, expensive, or unavailable. The total oxidizable precursor (TOP) assay represents one option to address the complexity associated with unknown PFAS precursors. In particular, the TOP assay transforms precursors into perfluoroalkyl acid (PFAA) endpoints via hydroxyl and sulfate radical-driven reactions. Solid samples, such as soil, sediment, and biosolids, contain high concentrations of reactive species scavengers that inhibit precursor oxidation; furthermore, PFAS extraction from solids involves solvent addition, which increases the potential for reactive species scavenging and necessitates further processing steps. The objective of this work was to improve the transformation efficiency, recovery efficiency, and throughput of the TOP assay for soil samples. Recovery efficiency was tracked via mass-labeled PFAA surrogates, which were not oxidized in TOP. Transformation efficiency was evaluated by introducing the M8-PFOSA surrogate standard into the original sample before extraction. PFAS, precursors, and mass-labeled surrogates were extracted with methanol, and the extracts were diluted with deionized water to 20% methanol. To improve transformation efficiency, solid-phase extraction with weak-anion exchange cartridges was used to remove background organic matter. Precursors were eluted with acetonitrile, evaporated, and reconstituted with TOP reagents. After 24 h at 85 °C, the PFAA end-products were present in saline water, affecting analytical compatibility and complicating enrichment. A QuEChERS extraction was employed by adding acetonitrile, magnesium sulfate, and sodium chloride. The acetonitrile-based extract was evaporated, reconstituted with internal standards, and analyzed for targeted PFAS. Recovery efficiency was dependent on chain length and ranged from 64 to 115%. The M8-PFOSA transformation efficiency was greater than 75% for over 20 soil samples from a PFAS-impacted site. Results showed ng g^-1 quantitation of over 30 PFAS, highlighting the strong performance of this modified TOP assay for real solid samples.