Analysis of Per- and Polyfluoroalkyl Substances in Groundwater by Direct Injection Using the Benchtop Multi- Reflecting Time-of-Flight Xevo™ MRT Mass Spectrometer

Significance of the Topic

The persistent nature and toxicity of per- and polyfluoroalkyl substances (PFAS) pose significant environmental and health concerns. Analytical methods that combine high resolution and high sensitivity enable comprehensive profiling and monitoring of these pollutants in water resources, supporting regulatory compliance and risk assessment.

Objectives and Study Overview

This study evaluates the direct injection workflow for PFAS analysis in groundwater using a benchtop multi-reflecting time-of-flight mass spectrometer. Key aims include assessing mass accuracy, sensitivity, dynamic range, and the instrument’s suitability for both targeted quantification and non-targeted screening in complex matrices.

Methodology and Instrumentation

An isotopic standard mixture of 30 PFAS compounds was serially diluted across a range of concentrations (1–10000 ng/L) and injected (10 µL) without cartridge-based extraction. Chromatographic separation employed an ACQUITY Premier LC system with PFAS kit and BEH C18 column followed by detection on a Xevo MRT Mass Spectrometer in negative ESI mode with data-independent acquisition (MSE). Mass calibration used dual lock masses and data were processed via the waters_connect platform with the UNIFI application.

Main Results and Discussion

The system achieved root-mean-square mass accuracy below 0.5 ppm over 535 measurements, with a symmetrical distribution centered near zero. Sensitivity allowed detection limits ≤5 ng/L for 24 compounds and as low as 1 ng/L for select analytes. Linear quantification spanned four orders of magnitude (1–10000 ng/L) with coefficients of determination above 0.98. Groundwater samples from the Channel Islands revealed five PFAS above EU thresholds, demonstrating the method’s capacity for real-world monitoring and the benefit of minimizing sample preparation bias.

Benefits and Practical Applications

• Combined targeted quantification and non-targeted screening enhances analytical depth.
• Direct injection reduces analysis time and potential extraction biases.
• High mass accuracy narrows candidate lists for confident compound identification.
• Wide dynamic range accommodates trace-level detection and high concentration quantification.

Future Trends and Opportunities

Increasing injection volumes and refining ion optics may further improve detection limits. Integration with complementary techniques like nuclear magnetic resonance or tandem MS could advance structural elucidation. Expanded spectral libraries and machine learning tools promise faster non-targeted PFAS discovery. Stricter regulations will drive method standardization and high throughput workflows.

Conclusion

The direct injection approach on a multi-reflecting TOF platform offers a robust, sensitive and accurate solution for PFAS analysis in groundwater. It fulfills regulatory requirements and supports comprehensive environmental surveillance with minimal sample preparation.

Reference

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