The use of aqueous film forming foams (AFFFs) containing per- and polyfluoroalkyl substances (PFASs) at Department of Defense (DoD) sites has led to potential PFAS contamination. This project will develop and validate improved analytical procedures for the comprehensive profiling of PFASs in AFFF-impacted environmental matrices and biological samples. With the exception of drinking water (EPA Method 537), standardized procedures for PFAS analysis in environmental samples are not yet available. While some in-house methods have been used routinely, they may not be transferable to newly-identified PFASs. The pre-existing methodologies may also show limited robustness with matrix variation. Since the suite of legacy PFASs likely does not capture all the dominant PFASs in AFFF-impacted sites, there is an urgent need for validated methods that can reliably encompass the breadth of anionic, cationic, and zwitterionic PFASs potentially occurring at such sites. The three specific objectives of this project are:
- Develop standardized analytical methods for compound-specific PFAS analyses that can achieve minimal matrix interferences and obtain appropriate accuracy, precision, and sensitivity;
- Develop robust procedures to determine total PFASs via Total Oxidizable Precursor (TOP) assay; and
- Develop robust procedures to determine total PFASs in terms of Total Extractable Organic Fluorine (TOF) content
Under Objective 1, standardized methods will be developed in water, soils and sediments, vegetation, and biota for 84 individual PFASs (48 quantitative analytes and 35 semiquantitative or qualitative analytes) using liquid chromatography (LC) coupled to mass spectrometry (MS/MS or HRMS). The quantitative analyte list covers all 24 PFASs from the SERDP and ESTCP Workshop Report. For method optimization purposes, the project will use AFFF-impacted field samples and/or background samples amended in-house with AFFFs and submit them to varied preparation procedures to obtain the desired sensitivity and suitable whole-method recovery. It will also evaluate and mitigate matrix effects on various LC-MS analytical platforms. Following method validation, further demonstration of the suitability for routine analysis will be conducted. A large series of field samples will be analyzed along with control samples as per DoD/Dpeartment of Energy (DOE) guidelines to ensure continued method validity (e.g., surrogate recoveries control charts when LC-MS is involved).
For the TOP assay in Objective 2, possible inconsistencies in oxidation yields of precursors into perfluorocarboxylates will be evaluated and mitigated. This will be critical for the whole-method accuracy, as will the delineation of a suitable clean-up and/or quantitation strategy.
Under Objective 3, a novel approach will be developed to determine TOF content using high-resolution continuum source atomic absorption spectrometry. The novel approach will be compared with combustion ion chromatography method and highlight any associated caveats.
The key outcome of this research is the establishment of standardized methods for individual PFASs and total PFAS approaches. This project will not only provide the standard operating procedures for various environmental matrixes, but also the results from the optimization and validation experiments. Providing guidance to end-users regarding the quantitation approach and potential limitations should also ensure the successful implementation of the methods to other laboratories in the future. Ultimately, the following questions will be answered:
- Are current analytical methods for legacy PFASs applicable as-is to the newly-identified analytes?
- What alternative analytical methods should be applied to reliably capture the larger scope of PFASs?
- Will the standardized methods ensure the robustness of process efficiency with matrix variation?
- Will the standardized methods be broadly transferable between different LC-MS technologies?
- What is the degree of flexibility (critical aspects vs. allowable changes) of the standardized methods?
- What can be the impact of using different calibration techniques on the whole-method accuracy?