Ultra-fast Trace Quantitation of PFAS in Drinking and Environmental Waters Using an Automated Sample Preparation and LC-MS/MS System

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are widely used in industrial and consumer applications due to their chemical stability and water repellence. Their persistence in the environment and potential toxicity have raised global concerns, driving the need for ultra-trace monitoring in drinking and environmental waters.

Objectives and Overview of the Study

This study aimed to develop and demonstrate a fully automated workflow for the trace quantitation of 62 PFAS compounds using minimal sample volumes. Key objectives included:

• Automated solid-phase extraction of 10 mL water samples
• Ultra-fast liquid chromatographic separation and tandem mass spectrometry (LC-MS/MS) analysis
• Achieving low-ppt detection limits for routine high-throughput monitoring

Methodology and Instrumentation Used

• Sample Preparation
  • Automated SPE on Biotage® Evolute® Express WAX using Extrahera™ system
  • Conditioning with 0.1% NH4OH in MeOH and 0.1% formic acid in water
  • Washing with 0.1% formic acid in 40% MeOH
  • Elution with 0.1% NH4OH in MeOH, evaporation, and reconstitution to 1 mL in 50% MeOH/H2O
• LC-MS/MS Analysis
  • Shimadzu Nexera X2 UHPLC coupled to LCMS-8060 triple quadrupole
  • Delay column (Shim-pack™ XR-ODS) upstream of analytical column (Shim-pack™ ODS III, 2.0×50 mm) to remove background PFAS
  • Mobile phases: aqueous buffer and methanol; gradient from 50% to 100% MeOH in 7 min at 0.4 mL/min
  • 250 µL injection, column at 40 °C, heated ESI in negative MRM mode

Main Results and Discussion

• All 62 PFAS, including linear and branched isomers, were resolved in a 7 min run with sharp peak shapes
• MRM transitions optimized for each analyte, eight-point calibration (0.0005–1 µg/L), linearity R2>0.99 for most compounds
• Preliminary method detection limits of 0.1 ppt for key PFAS such as PFOS and PFOA
• Real tap water analysis revealed PFOS and PFOA at 0.86 ppt and 1.80 ppt respectively
• An alternative online trapping approach showed potential for direct analysis of 2 mL samples

Benefits and Practical Applications

• Automated SPE reduces manual handling and improves reproducibility
• Low sample volume and fast turnaround support high-throughput environmental monitoring
• Ppt-level sensitivity meets stringent regulatory requirements for drinking water safety
• Capability to separate structural isomers enhances analytical specificity

Future Trends and Potential Applications

• Complete method validation: recovery, repeatability, precision
• Expansion to additional PFAS and emerging analogues
• Integration of online trapping for further automation and reduced solvent use
• Application to complex matrices such as soil, sediment, and biological samples
• Coupling with high-resolution mass spectrometry for untargeted screening

Conclusion

The presented workflow demonstrates a robust, automated sample preparation combined with ultra-fast LC-MS/MS capable of quantifying 62 PFAS compounds at sub-ppt levels in drinking and environmental waters. Ongoing validation efforts will further establish this approach for routine monitoring and regulatory compliance.

References

• No references were provided in the source text