Analysis and Quantitation of Polyfluorinated Alkyl Substances (PFAS) in EPA Method 537.1 Using High Resolution Accurate Mass Spectrometry

Importance of the Topic

Per- and polyfluorinated alkyl substances are persistent environmental contaminants regulated by EPA Method 537.1. Accurate detection and quantitation at low parts per trillion levels are essential for safeguarding drinking water quality and understanding emerging PFAS threats.

Objectives and Study Overview

• Assess high resolution accurate mass QTOF performance for quantitation of PFAS in EPA Method 537.1
• Compare quantitative results to a conventional triple quadrupole MS
• Demonstrate an untargeted workflow for identifying unknown PFAS in environmental samples

Methodology and Instrumentation

• Sample preparation following EPA Method 537.1 solid phase extraction protocol
• Chromatography using Nexera-X2 UHPLC with a Shim-pack XR-ODS delay column and Shim-pack TM Velox analytical column
• Electrospray ionization in negative mode on LCMS-8045 triple quadrupole and high resolution QTOF instruments
• MRM transitions optimized on the QQQ and high resolution MRM acquisition on the QTOF
• Data processing in LabSolutions Insight Explore with steps for feature detection, formula prediction, and MS/MS confirmation

Main Results and Discussion

• Quantitation limits for the QTOF equivalent to a triple quadrupole, detecting PFAS at 2–5 ppt
• Calibration linearity (r2 > 0.99) and accuracy meeting EPA criteria at 25 ppt level
• High resolution data enabled tentative identification of unknown PFAS such as a m/z 262.9751 compound predicted as C5HO2F9 and matched against DSSTox candidates

Benefits and Practical Applications

• QTOF delivers comparable quantitative performance to QQQ for regulated PFAS analysis
• Simultaneous qualitative screening of non-target PFAS simplifies laboratory workflows
• Supports routine monitoring and rapid investigation of emerging PFAS in water

Future Trends and Potential Applications

• Expansion of PFAS databases and spectral libraries to enhance non-target identification
• Integration of high-resolution workflows into regulatory methods with dynamic compound inclusion
• Application of HRAM screening approaches to diverse environmental and biota matrices

Conclusion

The study demonstrates that high resolution accurate mass QTOF analysis achieves equivalent quantitation to a triple quadrupole for PFAS in EPA Method 537.1 while providing added capability for non-target PFAS discovery, offering a flexible approach for comprehensive water quality monitoring.

References

1. EPA Method 537 rev 1.1 Determination of Selected Perfluorinated Alkyl Acids in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry U.S. EPA 2009
2. EPA Method 537.1 Version 1.0 Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry U.S. EPA 2018