Accurate Analysis of PFOA, PFHxS, and PFOS in Drinking Water Using a Triple Quadrupole LC/MS/MS

Significance of the Topic

Perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic acid (PFHxS) are persistent organofluorine compounds widely used in industrial and consumer applications. Their stability and resistance to degradation raise concerns about bioaccumulation and human exposure via drinking water. Accurate, low-level quantitation of these compounds is essential for water quality monitoring and compliance with regulatory standards.

Objectives and Study Overview

The study aimed to develop and validate a sensitive, reliable LC–MS/MS method for simultaneous determination of PFOA, PFOS and PFHxS at sub-nanogram-per-liter levels in drinking water. Method optimization focused on sample pretreatment, chromatographic separation and mass spectrometric detection to achieve a limit of quantitation of 0.2 ng/L in real water samples concentrated 1000-fold.

Methodology and Instrumentation

The procedure involved adding a 13C-labelled internal standard mix (final 10 ng/L) to 500 mL water, followed by anion-exchange solid-phase extraction and nitrogen-blow concentration to 0.5 mL in methanol. Automation of the extraction and concentration steps was performed using the AquaTrace system.

• UHPLC: Nexera-X3 with Shim-pack GIST-HP C18-AQ column (150 × 2.1 mm, 3 µm) and Shim-pack XR-ODS II delay column to minimize PFAS contamination.
• Mobile phase: 10 mM ammonium acetate in water (A) and acetonitrile (B) with a gradient from 40 % to 100 % B over 21 min; flow rate 0.2 mL/min; column at 40 °C.
• MS/MS: Shimadzu LCMS-8050RX triple quadrupole with CoreSpray technology, ESI negative mode, MRM transitions for analytes and isotope standards, optimized gas flows and temperatures.

Key Results and Discussion

Chromatographic conditions achieved clear separation of native and branched PFOS isomers. Calibration curves over 0.2–20 µg/L (equivalent to 0.2–20 ng/L in water) showed excellent linearity (R > 0.9996). At the lowest calibration point (0.2 µg/L), intra-day repeatability was <5 % RSD and accuracy between 80 % and 120 %. Recovery tests of spiked drinking water (1 and 5 ng/L) yielded recoveries of 82–103 % and repeatability <4 % RSD, confirming method robustness.

Benefits and Practical Applications of the Method

The optimized method provides:

• Sensitivity to detect PFAS at 0.2 ng/L in drinking water.
• High accuracy and precision suitable for routine monitoring.
• Automated sample handling reducing labor and variability.
• Enhanced contamination control via delay column and PFAS-grade reagents.

Future Trends and Potential Applications

Anticipated developments include expansion to a broader suite of emerging PFAS, integration with high-resolution mass spectrometry for structural elucidation, miniaturized or field-deployable platforms for on-site monitoring, and greener sample preparation techniques to reduce solvent use. Data analytics and machine learning may further improve quantitation and trend analysis.

Conclusion

The described LCMS-8050RX method enables sensitive, reliable quantitation of PFOA, PFOS and PFHxS in drinking water at sub-ng/L levels. CoreSpray technology and automated extraction ensure consistent ionization and high throughput. This approach supports regulatory compliance and protects public health through improved PFAS surveillance.