Formatted Title
Challenges and Lessons Learned in Validating a PFAS Suspect Screening Workflow
Background/Objectives
Per- and polyfluoroalkyl substances (PFAS) are a large group of compounds, of which, only a very few suitable reference standards are available for targeted analysis. For identifying, characterizing, and quantifying the unknown PFAS in legacy and next generation products, there is a need for high resolution mass spectrometric analytical techniques. This information will be critical to understanding and assessing the environmental fate and effects. The work presented here aims to provide a comprehensive method for the analysis of PFAS and related compounds using a suspect screening and non-targeted approach.
Approach/Activities
Suspect screening using a curated list of analytes is an advanced analytical tool to explore the nature and extent of PFAS contamination in the environment beyond the few dozen analytes with commercially available standards. Challenges in the literature on how best to prepare samples for a non-targeted method led to exploring separate water and soil validation studies. Suspect screening method development efforts focused on both the sample extraction and the analytical method development to cover wide range of PFAS- anionic, cationic, zwitterionic species. These tests were conducted in both aqueous and the solid matrices by spiking targeted analytes and the AFFF spikes in laboratory controls and environmental sample. Data processing approaches were developed to address key challenges: (a) Nomenclature and identification of suspect analytes of interest; (b) Creating appropriate data filters for data processing; (c) Assigning confidence levels to detections in an efficient, repeatable manner. Finally, semi-quantitation strategies, to offer approximate concentrations, vary in the literature and have led to multiple approaches of different complexities.
Results/Lessons Learned
The approach developed a curated list of suspect analytes and validated extraction, analysis and data work-up procedures to ensure meaningful, repeatable data output. The results of the validation studies in two different matrices has shown the sufficiency of an EPA Method 1633 approach for sample extraction, even for zwitterionic and cationic species. Furthermore, analyst-to-analyst and injection-to-injection variability has shown to be acceptable. Along the way, certain “tricks of the trade,” like common near-isobar pairs, will be presented from years of using this workflow.