A Comprehensive Workflow for PFAS Analysis in Wastewater with Extended EPA Draft Method 1633 List

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly stable, bioaccumulative contaminants found in wastewater. Their persistence in the environment and potential health risks make accurate, trace-level analysis essential for regulatory compliance and environmental monitoring.

Objectives and Study Overview

The study aimed to extend the EPA Draft Method 1633 to include 88 native and labeled PFAS compounds. It focuses on developing a reliable, high-throughput workflow that integrates sample preparation, LC-MS/MS analysis, and automated reporting to quantify PFAS in complex wastewater matrices.

Methodology and Instrumentation

Sample Preparation:

• Fortify 500 mL wastewater with native and isotopically labeled PFAS at defined concentration levels.
• Adjust pH to 6.0–7.0, spike with internal standards, and perform off-line SPE using Agilent Bond Elut PFAS WAX cartridges.
• Elute with acidified methanol, add carbon cleanup, centrifuge, and filter through Captiva Premium nylon syringe filters.

Instrumentation:

• Agilent Infinity II 1290 HPLC equipped with a PFC-Free Conversion Kit.
• ZORBAX Eclipse Plus C18 analytical (2.1×100 mm, 1.8 μm) and guard (2.1×5 mm, 1.8 μm) columns plus PFC Delay Column.
• Agilent 6495C triple quadrupole LC/TQ mass spectrometer operating in negative electrospray ionization mode.

Chromatographic Conditions:

• Flow rate 0.4 mL/min, column temperature 40 °C, injection volume 2 µL.
• Gradient from 2 % to 95 % ACN over 10 min, total run 12.2 min.

Key Results and Discussion

Recovery and Precision:

• Reagent water and wastewater recoveries for all native PFAS and EIS averaged close to 100 %, with RSDs below 5 % (EPA 1633 acceptance ±20 %).

Calibration and Detection Limits:

• Calibration curves for EPA-listed PFAS exhibited R² >0.998 over seven concentration levels.
• Method detection limits met or exceeded EPA 1633 draft requirements, with relative standard errors below 10 %.

Instrument Robustness:

• Over 300 consecutive injections of spiked wastewater showed consistent signal stability. Representative PFAS across the chromatographic range had RSDs below 6 %.

Benefits and Practical Applications of the Method

The workflow provides:

• High accuracy and precision for regulatory compliance and routine monitoring.
• Robustness against matrix effects in complex wastewater samples.
• Automated data handling and reporting through SLIMS to reduce manual errors and improve throughput.

Future Trends and Opportunities

Opportunities for enhancement include:

• Integration with high-resolution MS for non-target and suspect screening of emerging PFAS.
• Miniaturized or on-line SPE approaches to further reduce solvent use and sample handling time.
• Advanced informatics for real-time data analysis and reporting to support regulatory decision-making.

Conclusion

The extended EPA 1633 workflow outlined offers a comprehensive, reproducible approach for quantifying a broad spectrum of PFAS in wastewater. It achieves regulatory detection limits, high recoveries, and robust instrument performance, supporting environmental monitoring and public health protection.

References

1 Agilent5994-5226EN. Analysis Of Per- And Polyfluoroalkyl Substances (PFAS) In Aqueous Samples Per EPA Draft Method 1633.