Extraction of Per/Polyfluoroalkyl Substances in Water Using Agilent Offline Solid Phase Extraction

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are widely used for their surfactant and repellent properties. Their environmental persistence and bioaccumulation pose significant health risks at trace levels in drinking water. Regulatory methods, such as EPA Method 537, set strict advisory limits and drive the need for robust extraction and analysis techniques.

Objectives and Study Overview

This study aims to extend EPA Method 537 by developing an offline solid phase extraction (SPE) procedure using Agilent weak anion exchange (WAX) cartridges. The method targets 30 PFAS analytes—including the 14 specified by EPA 537 and 16 additional compounds—in larger-volume water samples (250 mL) to enhance sensitivity and throughput.

Methodology and Instrumentation

The procedure involves:

• pH adjustment of 250 mL water to 1–2 with glacial acetic acid
• Conditioning WAX cartridges with 60/40 ACN/MeOH + 5 % NH₄OH, water, and 1 % acetic acid
• Sample loading at ~10 mL/min, followed by vacuum drying and dual MeOH/NH₄OH elutions
• N₂ evaporation to ~500 µL, reconstitution to 1 mL in 96 % MeOH, and internal standard spiking

The analysis was performed on an Agilent 1260 Infinity II LC coupled to a 6470 triple quadrupole MS/MS with Jet Stream ESI in negative mode.

Main Results and Discussion

Recovery and precision were evaluated in LC-grade and municipal tap water:

• All 14 EPA 537 compounds showed recoveries of 70–130 % with RSD <15 %
• Among 16 additional PFAS, most achieved >70 % recovery; four FTA-e and related compounds yielded 40–70 % recovery
• No significant matrix effects were observed between purified and tap water

Trace blank contamination, notably PFBA, was traced to SPE materials but remained manageable through background subtraction.

Benefits and Practical Applications

This WAX SPE protocol offers:

• Expanded analyte coverage beyond EPA 537 to include emerging PFAS classes
• Improved sensitivity for low-level drinking water analysis
• A simple offline workflow compatible with standard LC/MS/MS platforms

It supports regulatory compliance monitoring and environmental research in diverse laboratory settings.

Future Trends and Opportunities

Ongoing developments may include:

• Automation of offline SPE steps to increase throughput
• Integration with high-resolution mass spectrometry for non-targeted PFAS screening
• Miniaturized cartridges and reduced solvent consumption for green analytics

Advances in sorbent chemistry and data processing will further broaden the scope of PFAS detection.

Conclusion

The modified offline WAX SPE method effectively quantifies 30 PFAS in drinking water, meeting EPA recovery criteria and demonstrating robustness across water matrices. This approach enhances laboratory capability for comprehensive PFAS monitoring.

Reference

1. Shoemaker J.; et al. EPA Method 537 LC/MS/MS for Perfluorinated Acids in Drinking Water. EPA/600/R-08/092.
2. Anumol T.; et al. Reduction of PFAS Background in Agilent LC Systems. Agilent Application Note 5991-7863EN.
3. Hunt K.; et al. PFAS Analysis by Agilent 6470 Triple Quadrupole LC/MS. Agilent Application Note 5991-7951EN.
4. Stevens J. Agilent SampliQ WAX Cartridges Technical Note 5990-5394EN.