Repeatability and Reproducibility of the Oasis™ WAX/GCB for PFAS Analysis Cartridges in Aqueous Samples for EPA Method 1633

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) pose serious environmental and health risks due to their persistence and bioaccumulative nature. Their detection in groundwater, surface water and wastewater is critical for protecting ecosystems and public health. With the US EPA Method 1633 extending PFAS analysis beyond drinking water, reliable sample preparation and analysis workflows are essential for regulatory compliance and environmental monitoring.

Objectives and Overview

This study evaluates the repeatability and reproducibility of Oasis WAX/GCB dual-phase cartridges for PFAS extraction from non-potable aqueous matrices in accordance with EPA Method 1633. The application note compares inter- and intra-batch performance across three production lots and six replicates per lot, ensuring the cartridges meet recovery and precision acceptance criteria.

Methodology and Instrumentation

Samples were prepared by solid-phase extraction (SPE) using Oasis WAX/GCB cartridges, combining weak anion exchange and graphitized carbon black sorbents in a single device. Eluted extracts were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) following the EPA 1633 procedure. The method workflow reduced manual steps and shortened preparation time by approximately 20%.

Used Instrumentation

• UPLC System: ACQUITY UPLC I-Class PLUS with 50 μL extension loop
• Analytical Column: ACQUITY Premier BEH C18 2.1×50 mm, 1.7 μm
• Isolator Column: Atlantis Premier BEH C18 AX 2.1×50 mm, 5.0 μm
• Mass Spectrometer: Xevo TQ-XS Triple Quadrupole
• Mobile Phases: 2 mM ammonium acetate in water (MPA) and acetonitrile (MPB)

Main Results and Discussion

All tested cartridges demonstrated recoveries and relative standard deviations (%RSD) within EPA Method 1633 acceptance criteria for 40 targeted PFAS. Both inter-batch and intra-batch precision were excellent, confirming lot-to-lot consistency and robust out-of-the-box performance. The dual-phase SPE device eliminated the need for separate cleanup steps without compromising analytical quality.

Benefits and Practical Application of the Method

• Streamlined workflow reduces manual handling and potential for error
• Time savings of up to 20% compared to separate WAX and GCB steps
• Performance-based flexibility for adaptation to various environmental matrices

Future Trends and Opportunities

Advances may include integration of high-throughput SPE automation, broader cartridge formats optimized for emerging PFAS precursors, and coupling with high-resolution instruments for non-targeted screening. Ongoing method validation across diverse matrices will support regulatory and research applications worldwide.

Conclusion

The Oasis WAX/GCB dual-phase SPE cartridges provide reliable, reproducible and efficient extraction for PFAS analysis under EPA Method 1633. Demonstrated repeatability across multiple lots and replicates ensures confidence in routine laboratory workflows for non-potable water monitoring.

Reference

1. US Environmental Protection Agency. Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS, Final version, 31 January 2024.
2. Organtini K., Rosnack K., Plummer C., Hancock P., Burt O. Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Accordance With EPA 1633 Part 2: Analysis of Aqueous Matrices, Waters Application Note 720008143, 2023.