PUSHING PFAS POSSIBILITIES: THE HUNT FOR ULTRA SENSITIVITY TO REACH PPQ EPA HEALTH ADVISORY LEVELS

Significance of the Topic

The family of per- and polyfluoroalkyl substances (PFAS) comprises chemically stable, bioaccumulative contaminants used in numerous industrial and consumer applications. Due to their persistence and potential health risks, regulatory bodies such as the US EPA have lowered drinking water advisory levels for key PFAS (PFOA, PFOS) to parts-per-quadrillion (ppq) concentrations. Achieving these ultra-low detection limits poses analytical challenges in both instrumentation sensitivity and mitigation of trace contamination during sample handling.

Objectives and Study Overview

This study aimed to develop and validate an analytical workflow capable of reliably quantifying PFOA, PFOS, PFBS and GenX at or below the stringent EPA health advisory levels (HALs) in drinking water. The approach combined solid-phase extraction (SPE) enrichment with high-sensitivity LC-MS/MS analysis, and was tested in two separate laboratories to demonstrate reproducibility under routine shared-space conditions.

Methodology

Samples were processed via SPE using Oasis WAX cartridges to achieve approximately 500× concentration enrichment. Key steps included cartridge conditioning, sample loading, washing to remove matrix interferences and elution of PFAS analytes under controlled, low-contamination conditions. Solvent and extraction blanks were analyzed in parallel to assess background levels.

Instrumentation

Analysis was performed using a Waters ACQUITY Premier UPLC System coupled to a Xevo TQ Absolute triple quadrupole mass spectrometer operating in negative electrospray ionization (ESI) mode. Chromatographic separation was achieved on a BEH C18 column (2.1×100 mm, 1.7 µm) at 35 °C with a water/methanol gradient containing 2 mM ammonium acetate. Key MS parameters included:

• Capillary voltage: 0.5 kV
• Desolvation temperature: 350 °C; gas flow: 900 L/hr
• Cone gas flow: 150 L/hr; source temperature: 100 °C
• Injection volume: 10 µL; sample temperature: 10 °C

Two independent labs (UK and US) ran identical methods to compare limits of quantitation (LOQs) and signal-to-noise performance.

Results and Discussion

Both laboratories achieved LOQs well below EPA interim HALs (0.004 ng/L for PFOA, 0.02 ng/L for PFOS), with calibration curves linear from 0.0005 to 0.08 ng/L (R² ≥ 0.992, residuals ≤ 30%). Solvent blanks showed no PFAS contamination. Extraction blanks revealed minor PFOA, PFOS and PFBS levels (4–21% of the lowest spike), all below one-third of the method reporting limit. Spiked recovery at HAL concentrations ranged from 90% to 111% with relative standard deviations of 2–13%, confirming method accuracy and repeatability at trace ppq levels.

Benefits and Practical Applications

The validated workflow demonstrates that standard analytical laboratories can meet or exceed current EPA PFAS guidelines without specialized infrastructure. Key advantages include:

• Ultra-trace sensitivity suitable for regulatory compliance
• High recovery and precision at sub-ppt spikes
• Minimal additional resource requirements beyond routine UPLC-MS/MS setups
• Emphasis on contamination control to ensure data quality

This approach supports environmental monitoring, water quality testing and compliance verification in public health and industrial settings.

Future Trends and Opportunities

Emerging directions include development of automated, miniaturized sample preparation platforms to further reduce contamination risk and sample volume, integration of high-resolution accurate-mass spectrometry for expanded PFAS screening, and adoption of digital data workflows to streamline regulatory reporting. Ongoing tightening of advisory limits will drive innovation in both analytical hardware and consumables designed for ultra-clean processing.

Conclusion

The combination of Oasis WAX SPE enrichment and highly sensitive Xevo TQ Absolute MS analysis provides a robust, reproducible method for quantifying PFAS at EPA health advisory levels in drinking water. Successful implementation in two independent laboratories underscores the practicality of achieving ppq-level detection in routine shared-space environments through meticulous sample handling and optimized instrument performance.

References

1. Dreolin N., Foddy H., Organtini K., Adams S., Rosnack K., Hancock P. Best practices for monitoring PFAS contamination in a routine shared-space commercial laboratory. Waters White Paper 720007905. 2023.
2. Shoemaker J., Tettenhorst D. Method 537.1: Determination of Selected Perfluorinated Alkyl Acids in Drinking Water by SPE and LC-MS/MS. US EPA, NCER; 2018.
3. Rosenblum L., Wendelken S. Method 533: Determination of PFAS in Drinking Water by Isotope Dilution SPE and LC-MS/MS. US EPA; 2019.