Accurate Mass Library for PFAS Analysis in Environmental Samples Using High Resolution GC/Q-TOF

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are a large class of persistent and bioaccumulative pollutants of global concern. Their unique properties, including environmental persistence, volatility, and potential toxicity, necessitate robust analytical methods to detect a wide range of PFAS in complex matrices such as soil and drinking water.

Objectives and Study Overview

This study aimed to develop and validate an accurate mass library for gas chromatography–quadrupole time-of-flight mass spectrometry (GC/Q-TOF) to enhance the detection and identification of both known and emerging PFAS in environmental samples. Secondary objectives included screening for additional contaminants in drinking water, such as disinfection byproducts and industrial chemicals.

Methodology and Instrumentation

• Sample Preparation
  • Soil from biosolid-amended fields in California extracted with methylene chloride.
  • Drinking water from two California locations (surface water and mixed source) extracted by multimode SPE and eluted with MTBE/MeOH, DCM, NH4OH and formic acid in EtAC:MeOH, concentrated and solvent-exchanged.
• GC/Q-TOF Analysis
  • Agilent 8890 GC coupled to 7250 high-resolution Q-TOF.
  • Inlet: 70 °C to 250 °C ramp, splitless 1 µL injection.
  • Columns: DB-5MS and DB-624, temperature programs optimized for PFAS separation.
  • Carrier gas: Helium at constant flow; transfer line 250 °C; source 200 °C; quadrupole 150 °C; electron energy 70 eV.
  • Spectral acquisition: 50–1200 m/z at 5 Hz.
• Data Processing
  • Deconvolution with MassHunter Unknowns Analysis using SureMass algorithm.
  • Library creation and compound ID via MassHunter Qualitative and PCDL Manager.
  • Statistical comparison in Mass Profiler Professional.

Main Results and Discussion

• Library Development
  • Compiled accurate mass EI spectra for over 100 PFAS compounds across diverse classes (PFAIs, FTIs, FTOHs, etc.).
  • Automated fragment formula annotation verified and incorporated into a GC/MS Personal Compound Database and Library (PCDL).
• PFAS Detection in Environmental Samples
  • Identified PFAS in soil and both drinking water sources using retention indices and accurate mass matches.
  • Representative compounds included ethyl perfluorobutyl ether in soil and methyl perfluorooctanoate in water.
• Screening for Additional Contaminants
  • Over 100 non-PFAS contaminants detected in drinking water, including disinfection byproducts, personal care chemicals, pharmaceuticals and pesticides.
  • Comparative analysis revealed source-dependent profiles (e.g. Irvine vs Weaverville), supported by volcano plot and targeted reprocessing for high-abundance compounds.

Benefits and Practical Applications

• High confidence PFAS identification facilitated by accurate mass library and high-resolution MS.
• Broader contaminant screening capability without additional sample injections.
• Applicability for environmental monitoring, regulatory compliance, and water quality assessment.

Future Trends and Potential Uses

• Expansion of the PCDL to include emerging and proprietary PFAS structures.
• Integration with targeted quantitation workflows for regulatory monitoring.
• Application to other complex matrices such as biota, sediments, and industrial effluents.
• Advancements in high-resolution GC/MS software for automated annotation and real-time screening.

Conclusion

The study demonstrates a comprehensive workflow for PFAS screening in environmental samples by combining high-resolution GC/Q-TOF analysis with an accurate mass spectral library. This approach enhances detection specificity, enables broad contaminant profiling, and supports environmental risk assessment efforts.