Adaptation of Large Panels of Per- and Polyfluoronated Alkyl Substances (PFAS) for Routine Analysis of Drinking and Environmental Waters by Direct Injection Using UHPLC-MS/MS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants with health risks at trace levels. They have contaminated soil, water and food, driving regulatory limits for drinking water. A comprehensive, sensitive routine method covering both the EU’s 20 regulated PFAS and the 47 required by the UK Drinking Water Inspectorate is essential for public safety and environmental monitoring.

Objective and Study Overview

This study adapts a direct injection UHPLC-MS/MS approach to quantify a broad panel of 48 PFAS in drinking and environmental waters. It aims to achieve low method detection limits, high throughput and robust performance across various water matrices.

Methodology

• Sample Preparation: Simple dilution (1:1) with acidified methanol and filtration through PFAS-free polypropylene GHP filters.
• Calibration: Matrix-matched, bracketed calibration over 0.5–200 ng/L (minimum six levels; 1/X weighting; R²≥0.99).
• Injection: Direct injection of 50 µL sample to minimize matrix effects and maintain sensitivity.
• Optimization: Balanced final organic content (50:50 water–methanol) for both short- and long-chain PFAS; optimized desolvation temperature for labile analytes.

Used Instrumentation

• UHPLC System: ACQUITY™ Premier with PFAS kit and isolator column.
• Analytical Column: ACQUITY UPLC™ CSH™ C18, 1.7 µm, 2.1×100 mm.
• Mass Spectrometer: Xevo™ TQ Absolute Tandem Quadrupole MS in UniSpray™ negative ion mode, MRM acquisition.
• Mobile Phases: 2 mM ammonium acetate in H₂O:MeOH (95:5) and in MeOH.
• Key Settings: Injection volume 50 µL; desolvation 400 °C; capillary voltage 0.9 kV; cone gas flow 150 L/hr; desolvation gas flow 900 L/hr; source temp 110 °C.

Main Results and Discussion

• Method Detection Limits (MDLs): 48 PFAS quantified with MDLs between 0.1 and 3.1 ng/L, meeting stringent regulatory requirements.
• Linearity and Matrix Effects: R²≥0.99 across soft, hard, mineral and river waters; quadratic calibration for PFHxDA and PFTrDS in select matrices.
• Accuracy and Precision: Recoveries and repeatability under 20% RSD for PFOA and PFTrDA at 10 ng/L across diverse water types.
• Chromatographic Robustness: PFAS-free kit and isolator column effectively delayed background interferences (e.g., PFBA), ensuring clear peak resolution.

Benefits and Practical Applications

• High Throughput: Rapid, minimal sample preparation and direct injection increase laboratory productivity.
• Low Contamination Risk: PFAS-free consumables and solvent lines reduce background bias.
• Extended Instrument Uptime: Reduced injection volumes prolong column and source life.
• Comprehensive Monitoring: Simultaneous detection of short- and long-chain PFAS with environmentally relevant sensitivity.

Future Trends and Applications

• Expansion of PFAS Panels: Inclusion of emerging compounds beyond current regulatory lists.
• Automation and Miniaturization: Further streamlining of sample preparation for field‐deployable platforms.
• High-Resolution MS Integration: Improved structural elucidation and non-target screening capabilities.
• Global Standardization: Harmonized methods for multi-laboratory comparability and regulatory alignment.

Conclusion

The direct injection UHPLC-MS/MS method on the Xevo TQ Absolute platform provides a robust, sensitive and efficient workflow for routine PFAS analysis. It achieves sub-ng/L detection limits across a wide PFAS panel while maintaining high throughput and low contamination risk.

Reference

• Jenny Davies, Waters Corporation. Adaptation of Large Panels of PFAS for Routine Analysis of Drinking and Environmental Waters by Direct Injection Using UHPLC-MS/MS.