DETECTION OF PFAS IN GROUNDWATER SAMPLE VIA SUSPECT SCREENING ANALYSIS WITH LC-HRMS/MS

PFAS (Per- and Polyfluoroalkyl substances) are emerging contaminants of concern due to their widespread presence in the environment, persistence, and potential toxicity. These synthetic organic compounds are structurally composed of hydrogen atoms that are completely replaced (perfluorinated) or partially replaced (polyfluorinated) by fluorine atoms. The strong stability of the C-F bonds makes these “forever chemicals” resistant to degradation under natural conditions. With over 4,700 compounds, PFAS are widely used in consumer products and industrial processes. However, despite their versatility, they can have toxic effects, accumulate in organisms, and biomagnify through the food chain. As unregulated substances with uncertain impacts, detecting PFAS in aquatic environments is essential for estimating human exposure. To achieve this, techniques like suspect screening, which enable the screening of thousands of compounds, can be applied (Brunn et al, 2023; Evich et al, 2022). In collaboration with the University of Arizona, a suspect screening method was developed for detecting PFAS compounds using LC-HRMS/MS (Liquid Chromatography coupled with High Resolution Mass Spectrometry). This method was applied to analyze groundwater from the Naval Air Station Joint Reserve Base Willow Grove (PA, USA). The analysis utilized UHPLC (Ultimate 3000, Dionex) coupled with tandem mass spectrometry (MS/MS, Orbitrap QExactive, Thermo Fisher Scientific) in a data-dependent acquisition (DDA) mode. The process began with a database containing a suspect screening list of 4,712 PFAS compounds from NIST (National Institute of Standards and Technology), which serves as the foundational dataset for identifying potential PFAS. The workflow combines the use of Trace Finder (TF) and Free Style (FS) software, along with external databases (m/z Cloud and PubChem). Initially, TF is used to screen precursor ions (MS¹) based on their m/z. At least one monoisotopic ion must be detected to ensure accurate identification, and the peak area of the detected compound must be evaluated. After precursor ion screening, the data are checked using FS to evaluate product ions (MS²). The MS² are analyzed to identify fragmentation patterns and compare them against external databases. After applying the current suspect screening method, 6 compounds (1H-Perfluoropentane, 1H-Perfluoroheptane, FPrSA, PFPrS, FBSA, and FHxSA) were found in the groundwater sample, indicating that more PFAS are present beyond the 25 already detected by the targeted analysis method routinely used in the laboratory. In the future, this method will be applied to more samples, and if necessary, the samples can be concentrated by solid phase extraction to maximize the detection of new PFAS.