Analysis of PFOS and PFOA in Tap Water

Significance of the Topic

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are widely recognized persistent organic pollutants with significant health and environmental impacts. Monitoring these compounds in potable water is critical for ensuring compliance with regulatory limits and protecting public health.

Objectives and Study Overview

This application note describes the development and validation of a sensitive and selective liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the determination of PFOS and PFOA in tap water. The goal is to achieve robust quantitation at trace levels suitable for regulatory and quality-control laboratories.

Methodology and Instrumentation

The analytical procedure combines reversed-phase ultra-high-performance liquid chromatography with electrospray ionization tandem mass spectrometry operating in negative ion mode.

• Chromatographic system: Shimadzu Nexera X3 UHPLC.
• Analytical column: Shim-pack Velox SP-C18 (150 mm × 2.1 mm i.d., 2.7 µm) with a Shim-pack XR-ODS II delay column (75 mm × 2.0 mm i.d., 2.2 µm) to prevent carryover.
• Mobile phases: A = 20 mmol/L ammonium acetate in water; B = methanol; gradient from 55% B at injection to 95% B at 25 min, held and returned to 55% B by 30 min; total runtime 34.5 min.
• Flow rate and temperature: 0.25 mL/min; column oven set to 40 °C; injection volume 50 µL.
• Mass spectrometer: Shimadzu LCMS-8060NX with ESI in negative mode; probe voltage –1 kV; focus voltage –3 kV; nebulizing gas 3 L/min; drying gas 10 L/min; heating gas 10 L/min; DL temperature 200 °C; heat block 300 °C; interface 200 °C.
• MRM transitions: PFOS m/z 498.90 → 79.95; PFOA m/z 412.90 → 169.10; internal standards 13C6-PFOS m/z 506.90 → 80.00 and 13C8-PFOA m/z 420.90 → 375.85.

Main Results and Discussion

The method provided baseline separation of PFOS and PFOA with sharp, symmetrical peaks and excellent repeatability. Calibration curves exhibited linearity over the target concentration range with correlation coefficients above 0.995. The use of isotope-labeled internal standards effectively compensated for matrix effects and instrumental variability. Method detection limits were low enough to meet stringent regulatory requirements for drinking water analysis.

Benefits and Practical Applications

This LC-MS/MS approach offers:

• High sensitivity and specificity for trace PFOS/PFOA quantitation.
• Robust performance with minimal carryover due to the delay column.
• Compatibility with routine water quality monitoring workflows.

Future Trends and Opportunities

Advances in high-resolution mass spectrometry and automated sample preparation are expected to further improve throughput and broaden the scope to include non-targeted screening of emerging per- and polyfluoroalkyl substances. Development of portable mass spectrometers may enable on-site environmental monitoring.

Conclusion

The described LC-MS/MS method using Shim-pack Velox SP-C18 and LCMS-8060NX instrumentation delivers reliable, sensitive, and reproducible analysis of PFOS and PFOA in tap water. It is well suited for laboratories tasked with compliance testing and environmental surveillance.

References

• Application News 01-00105 (JP, ENG), Shimadzu Corporation, First Edition: Sep. 2024.