Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water and Milk using LC-MS/MS coupled with Online-SPE Interface

Significance of PFAS Analysis

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants used in various industrial and consumer applications such as water repellents, fire-fighting foams and surface treatments. Their strong carbon-fluorine bonds confer high stability, leading to global distribution in water, soil and wildlife. Human exposure via drinking water and food raises health concerns, driving the need for sensitive and reliable analytical methods to monitor PFAS at trace levels.

Objectives and Study Overview

This study aimed to develop a rapid and automated method for the quantitative determination of 43 PFAS in tap water, bottled drinking water and milk. By integrating online solid-phase extraction (SPE) with LC-MS/MS and automated pretreatment using the SPL-W100 platform, the workflow targeted reduced sample handling, shortened analysis time and compliance with regulatory limits set by bodies such as the US EPA and AOAC.

Methodology and Instrumentation

Sample preparation for water involved mixing equal volumes of sample and methanol, followed by online SPE using a WAX cartridge on the SPL-W100. Milk samples were extracted via a QuEChERS-based protocol: acetonitrile and formic acid addition, Supel QuE cleanup, centrifugation and automated SPE. The purified extracts were analyzed by LC-MS/MS under negative electrospray ionization and MRM mode. Chromatographic separation was achieved on a Shim-pack Scepter C18 column with a gradient of aqueous ammonium acetate and acetonitrile over an 11-minute run.

Used Instrumentation

• SPL-W100 automated pretreatment system (AiSTI SCIENCE)
• LCMS-8060RX triple quadrupole mass spectrometer (Shimadzu)
• Shim-pack Scepter C18 analytical column (100 mm × 2.1 mm I.D., 3 µm)

Main Results and Discussion

All 43 PFAS eluted within 11 minutes, demonstrating efficient separation. In water matrices, calibration curves showed linearity from 0.0004 to 0.01 µg/kg for PFOA, PFNA, PFHxS and PFOS, and up to 0.1 µg/kg for other PFAS. Spiked recovery tests at 0.0004, 0.004 and 0.001 µg/kg yielded recoveries between 92 and 132 % with relative standard deviations below 15 %. In milk, calibration ranges were 0.005 to 1 µg/kg for major PFAS and 0.05 to 1 µg/kg for others. Recovery studies at 0.01, 0.1 and 1 µg/kg for key analytes produced recoveries of 79 to 113 % and RSDs under 9 %. Limits of quantitation met EPA and AOAC criteria. Analysis of real tap water samples quantified PFOA at 1.09 µg/kg, PFNA at 0.44 µg/kg, PFHxS at 0.40 µg/kg and PFOS at 0.63 µg/kg. No PFAS exceeded detection limits in bottled water and milk.

Benefits and Practical Applications

• Automated SPE and pretreatment reduce manual labor and risk of contamination.
• Rapid throughput enables high sample capacity for routine monitoring.
• Sensitivity and precision meet stringent regulatory requirements for water and food safety.

Future Trends and Potential Applications

• Extension to non-targeted screening of emerging PFAS using high-resolution mass spectrometry.
• Miniaturized and on-site SPE platforms for field analysis.
• Integration of data processing algorithms and AI for automated anomaly detection and trend monitoring.
• Application to broader matrices such as soil, biota and industrial effluents.

Conclusion

The combination of online-SPE automated sample preparation and LC-MS/MS provides a robust, rapid and sensitive method for the determination of 43 PFAS in drinking water and milk. The workflow achieves regulatory LOQs, reliable recoveries and reproducibility, supporting routine environmental and food safety surveillance.