Evaluation of SW-846 EPA 8327: Per-and Polyfluoroalkyl Substances (PFAS) Multi-Laboratory Validation Data By Recovery Correction and Approximate Isotope Dilution Recalculation

Polyfluoroalkyl Substances (PFAS) in the Environment (Session 2)
Oral Presentation

Prepared by T. Strock1, T. Strock2
1 - US EPA, United States Environment Protection Agency , 1301 Constitution Ave NW, Washington D.C., D.C., 20460, United States
2 - U.S. EPA, 1301 Constitution Ave NW, Washington D.C., D.C., 20460, United States


Contact Information: [email protected]; 202.566.0504

ABSTRACT

SW-846 EPA 8327: Per- and Polyfluoroalkyl Substances (PFAS) by Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS) is a determinative method for the quantification of PFAS, which can be used after EPA 3512, a simple solvent dilution sample preparation method. These methods were published in July 2021 and were validated together in groundwater, surface water, and wastewater matrices for 24 PFAS target analytes along with 19 isotopically labeled analogs used as surrogates. Despite having met the goals EPA defined for precision and bias in the validation study samples using external standard calibration, the most common theme in received public comments was to include isotope dilution/extracted internal standard calibration either as an option or exclusively in Method 8327. Therefore, we conducted a post-hoc analysis of the validation study data by either re-modelling the study sample and QC data based on an approximate isotope dilution/extracted internal standard calibration model or by recovery correcting the external standard calibration data. We then compared performance to results calculated by external standard calibration. These comparisons generally showed similar performance in terms of average recovery and within- and between-laboratory precision for most target analytes, with some reductions in bias and/or improvements in precision in the recalculated results for certain analytes, mainly for short- and long-chain perfluoroalkyl acids. These comparisons demonstrate that isotope dilution/extracted internal standard or recovery correction quantification schemes would have resulted in similar outcomes for the validation study, and they support inclusion of these options in Method 8327 as alternatives to external standard calibration, provided all method- and project-specified quality control acceptance criteria can routinely be met.