Simplifying EPA 1633 analyses with an improved dual bed solid-phase extraction methodJason

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) represent a class of persistent organofluorine compounds linked to adverse health outcomes. EPA Method 1633 establishes guidelines for the quantification of 40 PFAS in aqueous, solid, and biological matrices. Robust sample preparation is essential to achieve reliable detection limits, accuracy, and precision required for environmental monitoring and regulatory compliance.

Objectives and Study Overview

This study aims to simplify and enhance EPA 1633 sample preparation by introducing a dual bed SPE format. Key objectives include:

• Reducing manual packing steps and labor by integrating filter aid within the SPE cartridge.
• Preventing cartridge clogging during high-solids sample processing.
• Maintaining or improving method detection limits (MDLs), accuracy, and precision across all target PFAS.

Methodology and Instrumentation

Samples consisted of 500 mL of deionized water or ASTM substitute wastewater doped with native PFAS standards (100–2500 ng/L pre-extraction). The workflow comprised:

• Dual bed WAX/GCB SPE cartridges pre-loaded with filter aid.
• Automated sample loading using a Thermo Scientific AutoTrace 280 PFAS System.
• Elution and cleanup without additional dispersive carbon steps.
• LC-MS/MS analysis on a Waters Xevo TQ-S coupled to ACQUITY Premier UPLC.

Analytical conditions:

• Column: 1.8 µm C18 (50 × 2.1 mm).
• Mobile phases: A—water with 5 mM ammonium acetate; B—methanol.
• Gradient: 20% B to 95% B over 6 min; total run 7.5 min.
• Flow rate: 0.4 mL/min; injection volume: 3 µL; column temp: 40 °C.
• Detection: negative ESI, scheduled MRM transitions for native and 13C-labeled standards.

Main Results and Discussion

Performance metrics met or exceeded EPA 1633 criteria:

• MDLs ranged from 0.07 to 2.32 ng/L across 40 PFAS.
• Accuracy spanned 77–125% of spiked values; precision (RSD) typically below 15%.
• Dual bed cartridges with filter aid enabled 100% extraction of 500 mL wastewater without clogging.
• Comparative tests showed only 41% volume extracted with glass wool and 6% without filter aid before cartridge blockage.

Benefits and Practical Applications

The integrated dual bed SPE approach offers:

• Streamlined workflow by eliminating manual glass wool packing and dispersive GCB cleanup.
• Enhanced robustness for high-suspended-solids matrices, reducing rework and downtime.
• Consistent compliance with MDL, accuracy, and precision requirements of EPA 1633.
• Simplified operation on automated SPE platforms for routine environmental and industrial PFAS monitoring.

Future Trends and Applications

Emerging directions include:

• Extension of the dual bed format to solid and tissue matrices.
• Integration with high-resolution mass spectrometry for non-target PFAS screening.
• Development of high-throughput or miniaturized SPE devices for field deployable workflows.

Conclusion

The improved dual bed WAX/GCB SPE cartridge with built-in filter aid simplifies EPA 1633 PFAS analysis, prevents clogging, and maintains required detection and performance criteria. This method enhances efficiency and reliability for laboratories conducting trace PFAS monitoring.

Reference

No external literature references were cited in the original document.