Analysis of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA) in Water Samples Using Reversed-Phase Liquid Chromatography (RPLC) with Suppressed Conductivity Detection

Importance of the Topic

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are persistent, bioaccumulative perfluorinated acids found in drinking water and environmental matrices. Their widespread use in stain-resistant coatings and industrial processes has raised health and regulatory concerns. Sensitive, selective, and cost-effective analytical methods are essential for routine monitoring of these contaminants.

Objectives and Study Overview

This work presents a reversed-phase liquid chromatography (RPLC) method with on-line sample concentration and suppressed conductivity detection for quantifying PFOA and PFOS in water. The approach aims to achieve low detection limits, a wide dynamic range, and reliable performance in complex matrices.

Used Instrumentation

• ICS-3000 chromatography system with DP dual-gradient pump and DC chromatography module
• AMMS-300 2-mm anion MicroMembrane suppressor
• WPS-3000 SL autosampler with 1000 µL syringe and six-port valve configuration
• MasterFlex peristaltic pump for regenerant delivery
• Acclaim PA2 analytical column (2.1 × 150 mm, 3 µm) with PA2 guard cartridge (4.3 × 10 mm, 5 µm)
• Conductivity detector cell (35 °C) and Chromeleon 6.70 control software

Methodology

Water samples (1 mL) are loaded onto a PA2 guard cartridge for preconcentration and matrix cleanup. Following a 2.5 min wash, the valve switches to elute analytes onto the analytical column. The mobile phase consists of acetonitrile and a borate buffer (100 mM H3BO3, 9 mM KOH, pH 8) under a stepped gradient profile. Suppressed conductivity detection is achieved using a 10 mN H2SO4 regenerant at 0.5 mL/min. Column temperature is maintained at 30 °C and the detector at 35 °C.

Main Results and Discussion

The method achieved limits of detection and quantitation of approximately 1 µg/L and 3 µg/L, respectively, for both PFOA and PFOS. A dynamic range from 1 to 40 000 µg/L was demonstrated. Calibration was quadratic between 2 and 200 µg/L (R2 > 0.99, 5–15% RSD) and linear up to 20 000 µg/L. Recovery tests in tap water yielded 98–101% for PFOA and 97–112% for PFOS at spike levels ≥ 2 µg/L. Critical factors include filter selection (PTFE or polysulfone filters avoided adsorption; nylon membranes caused loss) and replacement of fluoropolymer flow-path components to prevent analyte adsorption. Direct injection of C6–C14 perfluorocarboxylic acids under similar conditions also provided good separation.

Benefits and Practical Applications

• Lower capital and operational costs compared to mass spectrometry
• High selectivity for anionic PFAS with suppressed conductivity
• Wide dynamic range suitable for regulatory monitoring and QA/QC
• On-line concentration and cleanup tailored for complex water matrices

Future Trends and Applications

Future developments may integrate this approach with mass spectrometric confirmation, expand analysis to shorter-chain PFAS and precursor compounds, miniaturize columns for faster throughput, and automate sample preparation to support high-volume environmental monitoring and industrial QA/QC.

Conclusion

The described RPLC method combining on-line preconcentration and suppressed conductivity detection provides a robust, sensitive, and economical solution for PFOS and PFOA quantitation in water samples. Its adaptability and performance make it suitable for routine environmental and regulatory applications.

References

1. Giesy JP, Kannan K. Environmental Science & Technology. 2001;35:1339.
2. Kissa E. Fluorinated Surfactants and Repellents. 2nd ed. Marcel Dekker; 2001.
3. Larson BS, Kaiser MA. Analytical Chemistry. 2007;79:3966.
4. Weiss J. Handbook of Ion Chromatography. 3rd ed.
5. Liu X, Bordunov A, Pohl C. Journal of Chromatography A. 2006;1119:128.
6. MicroMembrane Suppressor 300 Manual. Dionex Corporation.
7. Nakayama SF. U.S. EPA, National Exposure Research Laboratory; personal communication.