Analysis of Per/Polyfluoroalkyl Substances in Water Using an Agilent 6470 Triple Quadrupole LC/MS

Significance of the Topic

Per- and polyfluoroalkyl substances (PFASs) are persistent, bioaccumulative, and toxic compounds widely used in industrial and consumer products. Their resistance to degradation and global distribution in water resources have raised regulatory concerns. Accurate and comprehensive analytical methods are essential to meet stringent guidelines and protect human health and the environment.

Study Objectives and Overview

This work aimed to develop and validate a single LC/MS/MS method for the quantitation of 30 PFASs across eight chemical classes in water. Key objectives included

• Extending the analyte list beyond the 14 compounds in EPA Method 537
• Demonstrating instrument performance for low-picogram detection
• Implementing strategies to minimize background contamination

Methodology

The analytical approach combined dynamic multiple reaction monitoring in negative electrospray mode with standardized calibrations:

• Analytes: 30 PFASs including perfluoroalkyl acids (C4–C14), sulfonates, fluorotelomer sulfonates, telomer acids, and sulfonamides
• Calibration: Six-point curves weighted by 1/x from 0.08 to 2.5 ng/L equivalents (extended range for fluorotelomer acids)
• Sample preparation: Mixing of individual stock solutions and serial dilutions in acetonitrile or methanol
• Detection: Agilent 6470 Triple Quadrupole LC/MS/MS using optimized precursor/product transitions and collision energies

Instrumentation

• LC: Agilent 1260 Infinity binary pump, autosampler, thermostated column compartment
• Column: ZORBAX Eclipse Plus C18 (3.0 × 50 mm, 1.8 µm) with a delay column (4.6 × 50 mm, 3.5 µm) to trap PFAS memory
• Mobile phases: 5 mM ammonium acetate in water (A) and in 95% methanol (B); gradient from 10% to 100% B over 14.5 min; flow 0.4 mL/min; injection 5 µL; column at 50 °C
• MS: Agilent 6470 Triple Quadrupole with Jet Stream ESI; gas temperature 230 °C; sheath gas 350 °C; optimized voltages and gas flows

Results and Discussion

• Linearity: R² between 0.992 and 1.000, meeting EPA/ASTM requirements
• Detection Limits: Instrument detection limits as low as 0.025 pg on-column; EPA LODs within Method 537 criteria
• Accuracy and Precision: Recoveries of 76–120% and %RSD below 15% at low pg levels
• Chromatography: Complete separation of 30 PFASs within a 16.5-min run time
• Background Reduction: Delay column installation and replacement of PTFE septa with polyethylene vials and caps effectively removed system PFAS memory

Practical Benefits and Applications

• Enables routine monitoring of an expanded PFAS panel in environmental and drinking water laboratories
• Supports compliance with low ng/L advisory limits for PFOA, PFOS, and related compounds
• Offers guidance on system configuration to minimize analytical artifacts
• Provides a flexible platform for emerging PFAS analytes

Future Trends and Opportunities

• Extension to novel PFAS classes and breakdown products
• Integration with high-resolution MS for non-target screening
• Development of harmonized global monitoring protocols
• Automation of sample prep and data processing for higher throughput

Conclusions

The validated Agilent 6470 LC/MS/MS method delivers robust, sensitive, and precise quantitation of 30 PFASs in water matrices. By expanding on EPA Method 537 and addressing contamination issues, this comprehensive protocol enhances environmental monitoring capabilities and supports regulatory compliance.

References

• T. Anumol et al. Recommended Plumbing Configurations for Reduction in Per/Polyfluoroalkyl Substance Background with Agilent 1260/1290 Infinity LC Systems. Agilent Technologies Application Note 5991-7863EN, 2017.