Direct analysis of selected per- and polyfluorinated alkyl substances (PFAS) in ground, surface, and waste water by LC-MS/MS

Importance of the Topic

Per- and polyfluoroalkyl substances are persistent environmental contaminants found in ground, surface, and wastewater. They resist degradation, bioaccumulate, and pose human health risks at trace levels. Monitoring in non-drinking water is vital for regulatory compliance and pollution control.

Objectives and Study Overview

This study aims to evaluate direct LC-MS/MS method performance for detecting 24 selected PFAS compounds at ng/L concentrations across diverse water matrices. Data support EPA 8327 interlaboratory validation without traditional extraction procedures.

Methodology and Instrumentation

A direct analysis approach mixes 5 mL samples with methanol and isotopic surrogates, followed by filtration and acidification. Separation uses a PFAS-free UHPLC system equipped with an isolator column and Accucore RP-MS analytical column set at 45 °C. Detection employs a TSQ Altis triple quadrupole mass spectrometer in negative ion mode with optimized SRM transitions. Mobile phases combine ammonium acetate, acetic acid, water, and methanol under a 21-minute gradient with 25 µL injections.

Main Results and Discussion

• Calibration linearity exceeds 0.99 over 5–200 ng/L. Residuals fall within 20%.
• Reporting limits range from 2 to 10 ng/L, up to five times lower than ASTM D7979 and EPA 8327 requirements.
• Method blanks show no detectable PFAS above half the LLOQ. LLOQ check samples meet signal to noise and recovery criteria.
• Recoveries across water matrices at 60 and 200 ng/L generally range between 70 and 130%. Lower recoveries for PFBA in wastewater indicate potential matrix suppression.
• Precision remains within 20% RSD for most compounds in all matrices, demonstrating robustness. Reducing injection volume improves peak shapes under high matrix loads.

Benefits and Practical Applications

The direct LC-MS/MS approach eliminates solid phase extraction, reducing sample preparation time and costs. It delivers sensitive, accurate quantitation of diverse PFAS in complex waters, supporting environmental monitoring programs and regulatory compliance with minimal matrix interferences.

Future Trends and Applications

Advancements may include coupling with online extraction for higher throughput, expanding target lists to novel PFAS, integrating high resolution and data processing algorithms, and developing portable MS platforms for in-field screening.

Conclusion

The method provides a fast, reproducible, and sensitive solution for comprehensive PFAS analysis in various water matrices. It meets stringent detection limits, offers robust performance, and facilitates interlaboratory validation of EPA 8327 for environmental monitoring needs.

Reference

1. National Institute of Environmental Health Sciences. Perfluorinated Chemicals PFCs fact sheet
2. US EPA PFAS overview web page
3. Agency for Toxic Substances and Disease Registry interim guidance for clinicians
4. Stahl T, Mattern D, Brunn H. Toxicology of perfluorinated compounds. Environ Sci Eur 2011;23:38
5. US EPA Method 537: PFAS in drinking water by SPE-LC-MS/MS
6. US EPA Unregulated Contaminant Monitoring Rule 3 description
7. ASTM D7979 Standard Test Method for PFAS in water by LC-MS/MS
8. US EPA Method 537.1 updated PFAS analysis procedure