Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous Samples Per EPA Draft Method 1633

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants with known adverse health effects. Reliable detection and quantification in aqueous matrices are essential for regulatory compliance, public health protection, and environmental monitoring.

Objectives and Overview of the Study

This study evaluated the performance of the US EPA Draft Method 1633 for PFAS analysis in aqueous wastewater samples. It focused on verifying extraction recoveries, method detection limits (MDLs), reproducibility, and demonstrating real-world applicability using Agilent Bond Elut PFAS WAX SPE cartridges and LC–MS/MS instrumentation.

Methodology and Instrumentation

Samples of 500 mL unpreserved reagent water and wastewater effluent were spiked with isotopically labeled internal standards and loaded onto Agilent Bond Elut PFAS WAX SPE cartridges conditioned with methanolic ammonium hydroxide and formic acid. Following washes with water and formic acid/methanol, analytes were eluted with 1 % methanolic ammonium hydroxide. A carbon S cleanup step removed co-extractives, and samples were filtered before analysis.
Analysis employed an Agilent 1290 Infinity II LC system with a ZORBAX Eclipse Plus C18 column and PFAS delay column, coupled to an Agilent 6470 triple quadrupole mass spectrometer operated in dynamic MRM negative electrospray mode.

Main Results and Discussion

In reagent water, surrogate recoveries ranged from 63 % to 121 % (RSD < 20 %). Initial MDLs for 40 target PFAS met or exceeded Draft Method 1633 requirements, often below 1 ng/L. Mid-level precision trials yielded RSDs under 9 % and recoveries between 70 % and 116 %.
Wastewater effluent analysis detected multiple PFAS, with PFHxA and 6:2 FTS up to 34 ng/L. Spiked effluent recoveries averaged 88 %–111 % for most analytes. Compounds without matched labeled standards (e.g., PFDS, PFDoS) showed lower recoveries (48 %–70 %), which improved when best-matching surrogates were applied.

Benefits and Practical Applications

• Standardized, high-throughput workflow for regulatory PFAS quantification across diverse aqueous matrices.
• Sensitive detection enables monitoring of trace-level PFAS in drinking water, wastewater, and environmental samples.
• Robust cleanup minimizes matrix interferences and extends column and instrument lifetime.

Future Trends and Possibilities

Final multilaboratory validation of EPA Method 1633 may refine SPE protocols and expand matrix scope. Development of additional isotopically labeled analogs will improve accuracy for currently underrepresented PFAS. Coupling this approach with high-resolution mass spectrometry and automated sample preparation can further enhance sensitivity, throughput, and data quality.

Conclusion

The demonstrated SPE and LC–MS/MS workflow meets or surpasses EPA Draft Method 1633 performance criteria for aqueous PFAS analysis. It provides reliable recoveries, low detection limits, and reproducible results, supporting environmental monitoring and regulatory compliance.

References

1. US EPA Draft Method 1633 for PFAS in Environmental Samples, June 2022.
2. Hunt K, Hindle R, Agilent Application Note 5994-4926EN, 2022.
3. Giardina M, Agilent Application Note 5994-4960EN, 2022.