Dispersive liquid-liquid micro-extraction for the automated sample preparation of PFAS in drinking water

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent pollutants of critical environmental concern due to their widespread use, bioaccumulation, and potential health risks. Sensitive, cost-effective monitoring of PFAS at low ng/L levels in drinking water is essential to meet stringent regulations and protect public health.

Objectives and Study Overview

This study demonstrates an automated workflow for sample preparation and pre-concentration of 56 PFAS compounds in drinking water using dispersive liquid–liquid microextraction (DLLME) on a Thermo Scientific TriPlus RSH SMART autosampler, coupled to HPLC-HRAM detection. The goal is to achieve high enrichment, reproducibility, and throughput while minimizing solvent use and manual labor.

Methodology and Instrumentation

Samples of drinking water (15 mL) were acidified, spiked with isotopically labeled internal standards, and subjected to a two-step DLLME protocol involving low- and high-density solvents under automated vortexing and centrifugation. The final extract (~30 µL) is compatible with LC-MS analysis. The key instruments and software included:

• Thermo Scientific TriPlus RSH SMART autosampler with automatic tool change, vortexer, and centrifuge modules
• Thermo Scientific Vanquish Flex HPLC system coupled to an Orbitrap Exploris 240 mass spectrometer
• Thermo Scientific Chromeleon 7.3.2 Chromatography Data System and DLLME workflow editor

Main Results and Discussion

The method delivered enrichment factors up to 500 for a 15 mL sample, achieved limits of quantification between 0.1 and 5 ng/L, and provided excellent linearity (R2 > 0.99) over 0.1–100 ng/L. Intra- and inter-day precision and accuracy for spiked tap and bottled water (5 and 75 ng/L) were within ±30% and <30% RSD. Cross-contamination was below 20% of the LOQ for most compounds, and stability tests demonstrated acceptable accuracy after 12 h in the autosampler and 24 h at 25 °C for extracts.

Benefits and Practical Applications

The automated DLLME approach reduces solvent consumption and sample volume, lowers per-sample cost by eliminating SPE cartridges, and increases laboratory throughput with minimal manual handling. High sensitivity and broad PFAS coverage support compliance with global regulations and enable routine monitoring in water quality and environmental laboratories.

Future Trends and Potential Applications

Further expansion of automated microextraction methods could target emerging PFAS and other trace contaminants in complex matrices such as wastewater and food. Integration with GC-MS workflows, enhanced label-free quantification strategies, and miniaturized extraction modules may drive greener, high-throughput environmental analysis.

Conclusion

The demonstrated automated DLLME protocol on the TriPlus RSH SMART platform offers a rapid, reliable, and eco-friendly alternative to conventional SPE for trace PFAS analysis in drinking water. It combines high enrichment, low contamination risk, and scalable throughput, meeting stringent analytical and regulatory demands.

Reference

1. Application Note 002902: Direct injection of drinking water for analysis of 54 PFAS by LC-MS/MS.
2. Application Note 73883: Automated SPE and LC-MS/MS for PFAS in drinking water (EPA 533).
3. Application Note 73346: Automated SPE and LC-MS/MS for PFAS in drinking water.
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