Direct Injection Analysis of Organofluorine Compounds (PFAS) by Triple-Quadrupole LC/MS/MS

Importance of the Topic

PFAS including perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and related compounds are widely used for their water and oil repellency properties, but their environmental persistence and potential health risks demand efficient monitoring.

Objectives and Overview of the Study/Article

The article aims to develop a direct-injection triple-quadrupole LC/MS/MS workflow to analyze PFOA, PFOS and 27 additional PFAS analogues without solid-phase extraction, focusing on simplifying sample preparation and enhancing throughput.

Methodology and Instrumentation

Standard solutions were prepared in a water/methanol (7/3) mixture. An impurity delay column was installed between the mixer and autosampler to separate system-derived PFOA from sample analytes. Two analytical protocols were validated: a 30-minute gradient for PFOA/PFOS quantification and a 5.5-minute high-throughput method for 29 PFAS compounds.

Used Instrumentation

• UHPLC System: Shimadzu Nexera Series
• Analytical Columns: Shim-pack Velox SP-C18 (150×2.1 mm, 2.7 µm) and Shim-pack ODS III (50×2.0 mm, 1.6 µm)
• Delay Columns: Shim-pack XR-ODS II (75×2.0 mm, 3 µm) and XR-ODS (30×3.0 mm, 2.2 µm)
• Mass Spectrometers: LCMS-8060 and LCMS-8050 triple quadrupole
• Ionization: Electrospray (Negative mode), MRM detection
• Critical Parameters: Gradient elution, flow rates 0.25–0.4 mL/min, column temperatures 40 °C, probe voltage –1 to –3 kV

Key Results and Discussion

Calibration for PFOA/PFOS was linear between 1–100 ng/L with R2 > 0.999. Accuracy ranged 91.4–101.5% and repeatability was below 6%. The high-throughput method resolved 29 PFAS compounds in a single 5.5-minute run with calibration ranges from 0.009 µg/L to 25 µg/L and R2 > 0.99 for all analytes.

Benefits and Practical Applications of the Method

• Elimination of solid-phase extraction simplifies workflow and reduces sample preparation time.
• High analytical throughput supports large-scale environmental or water quality monitoring.
• Sensitive and reproducible quantification at low ng/L levels meets regulatory requirements.

Future Trends and Potential Applications

Further expansion to novel PFAS classes and integration with high-resolution mass spectrometry could broaden environmental surveillance. Automation and miniaturization may enable on-site rapid screening of water and biological samples.

Conclusion

The presented direct-injection LC/MS/MS method offers a fast, robust, and sensitive approach for simultaneous quantification of major PFAS compounds without extensive pretreatment, facilitating compliance monitoring in environmental and industrial contexts.