Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Accordance with EPA 1633 Part 3: Analysis of Soil and Tissue

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly persistent contaminants of increasing regulatory concern. Robust analytical methods for quantifying PFAS in complex matrices such as soils and biological tissues are essential for environmental monitoring, remediation efforts, and compliance with US EPA requirements.

Objectives and Study Overview

This application study demonstrates a comprehensive end-to-end workflow for PFAS analysis in soil and fish tissue following US EPA Method 1633. The main goals are to:

• Adapt the sample preparation to a bilayer dual-phase SPE cartridge combining weak anion exchange (WAX) and graphitized carbon black (GCB)
• Validate performance against EPA 1633 criteria for extracted internal standards (EIS) and target analyte recoveries
• Assess accuracy using a certified soil reference material

Methodology and Instrumentation

Sample Preparation and Cleanup

• Soil: Custom PFAS-spiked soil reference material; fish tissue: homogenized salmon
• Dual-phase SPE cartridge (Oasis GCB/WAX) stacking GCB atop WAX to replicate the dispersive GCB cleanup step
• Internal standards spiked before and after extraction according to EPA 1633 guidelines

Liquid Chromatography–Mass Spectrometry

• LC System: ACQUITY™ Premier BSM FTN UPLC with PFAS kit and isolator column
• Analytical Column: ACQUITY Premier BEH C18, 2.1×50 mm, 1.7 µm
• Mobile Phases: 2 mM ammonium acetate in water (A) and acetonitrile (B); flow rate 0.3 mL/min
• MS System: Xevo™ TQ Absolute tandem quadrupole; ESI⁻ ionization; MRM acquisition

Key Results and Discussion

Recovery Performance

• Extracted internal standard recoveries averaged 81 % for soil and 85 % for tissue (n=3), with RSDs of 2.8 % and 9.2 % respectively
• All target PFAS recoveries fell within the EPA 1633 acceptance limits

Accuracy Assessment

• Analysis of a certified PFAS soil reference material yielded mean trueness of 97 % (range 85–120 % of certified values)

These results confirm that the bilayer SPE approach is equivalent to the multi-step dispersive GCB/WAX procedure while improving ease of use and reducing contamination risk.

Benefits and Practical Applications

• Simplified sample preparation by integrating cleanup sorbents into a single cartridge
• Time savings and reduced potential for PFAS contamination during handling
• Demonstrated compliance with regulatory performance criteria for soils and biological tissues

Future Trends and Applications

Anticipated developments include automation of SPE workflows, expansion to additional environmental and food matrices, high-throughput screening with enhanced UPLC–MS/MS platforms, and integration of green extraction techniques to minimize solvent usage.

Conclusion

The validated workflow using a bilayer Oasis GCB/WAX cartridge coupled with ACQUITY Premier UPLC and Xevo TQ Absolute MS meets all EPA 1633 performance requirements for soil and fish tissue PFAS analysis. This streamlined approach offers equivalent accuracy and precision to conventional methods while reducing preparation time and contamination risk.

Reference

1. US EPA, Analysis of PFAS in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS (Method 1633), Jan 2024.
2. US EPA, Clean Water Act Analytical Methods for PFAS, Jan 2024.
3. Organtini K.L., Rosnack K.J., Hancock P., Application of EPA 1633 Part 1, Waters Application Note 720008117, 2023.