Ultra-Trace Detection of Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water to Meet New US EPA Interim Health Advisory Levels

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are a large group of highly persistent synthetic chemicals that bioaccumulate in humans, wildlife and the environment. Their extreme stability and widespread use in industrial and consumer products have led to growing concerns over their health impacts and environmental persistence. As regulatory bodies tighten advisory and enforceable limits for PFAS in drinking water, analytical methods capable of ultra-trace detection have become essential to ensure public safety and compliance.

Objectives and Study Overview

This study aimed to develop and validate a robust analytical workflow for the detection of key PFAS—PFOA, PFOS, PFBS and GenX—in drinking water at concentrations below the 2022 US EPA Interim Health Advisory Levels. By combining solid-phase extraction (SPE) enrichment with ultra-performance liquid chromatography and tandem mass spectrometry, the method seeks to achieve limits of quantitation in the parts-per-quadrillion range under routine laboratory conditions.

Methodology and Instrumentation

Water samples were handled in a controlled laboratory environment with rigorous screening of all consumables and reagents to minimize background PFAS contamination. An extraction internal standard mixture containing 13C-labeled analogues was spiked prior to SPE using Oasis WAX cartridges, providing a 500× enrichment factor. After elution and concentration, an injection standard was added during reconstitution. Chromatographic separation was performed on a Waters ACQUITY Premier UPLC fitted with a BEH C18 column (2.1 × 100 mm, 1.7 μm) using a gradient of 2 mM ammonium acetate in water and methanol at 0.3 mL/min. Detection employed a Waters Xevo TQ Absolute triple quadrupole mass spectrometer in negative electrospray ionization mode with multiple reaction monitoring. Data acquisition and quantitation were carried out using waters_connect for Quantitation software.

Used Instrumentation

• Waters ACQUITY Premier UPLC system
• Waters Xevo TQ Absolute triple quadrupole mass spectrometer
• Waters_connect for Quantitation software
• Oasis WAX solid-phase extraction cartridges

Main Results and Discussion

The workflow achieved limits of quantitation well below the updated EPA advisory levels: 0.001 ng/L for PFOA, PFOS and PFBS, and 0.004 ng/L for GenX. Calibration curves spanning 0.0005 to 0.08 ng/L were linear with correlation coefficients ≥0.992. Solvent and extraction blanks confirmed minimal background interference, with any detected contamination representing less than one-third of the minimum reporting levels. Method recoveries ranged from 90% to 111%, with relative standard deviations between 2% and 13% across two independent laboratories, demonstrating excellent accuracy and precision at sub-ppt concentrations.

Benefits and Practical Applications

• Reliable sub-ppt detection of priority PFAS compounds to support compliance with stringent advisory limits
• A fully integrated workflow minimizing contamination risks and simplifying routine monitoring
• Comprehensive solution including standards, consumables, instrumentation, software and training

Future Trends and Applications

As regulatory frameworks continue to evolve and extend to additional environmental and food matrices, analytical methods will need to deliver even greater sensitivity, throughput and contamination control. Advances in automation, high-sensitivity mass spectrometry and data analytics are expected to enable broader, more efficient PFAS surveillance and remediation strategies.

Conclusion

This study demonstrates that combining targeted SPE enrichment with the high sensitivity of the Xevo TQ Absolute mass spectrometer enables reliable detection of PFAS at sub-ppt levels in drinking water using standard laboratory resources. Meticulous contamination control and rigorous method validation ensure data quality and regulatory compliance for ultra-trace PFAS monitoring.

References

• De Silva AO, Armitage JM, Bruton TA et al. PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps. Environmental Toxicology and Chemistry. 2021;40(3):631–657.
• US EPA. Drinking Water Health Advisories for PFOA and PFOS. 2022.
• US EPA. PFOA & PFOS Drinking Water Health Advisories Fact Sheet. 2016.
• European Parliament and Council. Directive (EU) 2020/2184 on the quality of water intended for human consumption. 2020.
• Organtini K, Rosnack K, Stevens D, Ross E. Analysis of Legacy and Emerging PFAS in Environmental Waters Using SPE and LC-MS/MS. Waters Application Note 720006471. 2019.
• Organtini K, Adams S. Improved Sensitivity for PFAS Detection in Environmental Water Samples Using Direct Injection on Xevo TQ Absolute. Waters Application Note 720007559. 2022.
• Shoemaker J, Tettenhorst D. EPA Method 537.1: Determination of Selected Perfluorinated Alkyl Acids in Drinking Water by SPE and LC-MS/MS. 2018.
• Rosenblum L, Wendelken S. EPA Method 533: Determination of PFAS in Drinking Water by Isotope Dilution Anion Exchange SPE and LC-MS/MS. 2019.