Novel, rapid, and flexible tandem dispersive liquidliquid microextraction for the determination of PFAS in environmental samples

Significance of the topic

The environmental and health concerns associated with per- and polyfluoroalkyl substances (PFAS) have driven strong demand for accurate, high-throughput analytical methods across diverse matrices (drinking water, groundwater, wastewater, soil, sludge, and industrial effluents). Regulatory frameworks (e.g., EU Drinking Water Directive, U.S. EPA Method 1633A) require sensitive, reproducible quantitation at low ng/L and ng/kg levels. Methods that reduce solvent use, operator exposure, and manual handling while preserving analytical performance are therefore highly valuable for routine and regulatory laboratories.

Objectives and study overview

This application note demonstrates an automated tandem dispersive liquid–liquid microextraction (DLLME) workflow for targeted analysis of 61 PFAS across multiple environmental matrices. Goals were to (1) streamline extraction, concentration and clean-up into a single automated process; (2) minimize solvent consumption and manual steps; (3) deliver regulatory-compliant sensitivity and robustness; and (4) show compatibility with both triple quadrupole SRM and high-resolution full-scan HRMS detection approaches.

Methodology

• Automated sample preparation: Tandem DLLME implemented on an autosampler platform (TriPlus RSH SMART) controlled by Chromeleon CDS 7.3.2; identical extraction protocol for all matrix types.
• Throughput and solvent use: Typical batch runs of 54 samples in ~8 hours (≈9 min/sample) with total solvent use ≈2 mL per sample (extraction + clean-up/injection solvent).
• Calibration and quantitation: Simplified matrix-extracted calibration curves (0.1–100 ng/L) using isotope-labeled internal standards; standard addition performed in parallel to verify matrix effects.
• Chromatography: Vanquish Duo UHPLC with Hypersil GOLD columns (C18 and C8 used for confirmation). Methanol/water mobile phases.
• Detection strategies: Two validated options—(A) targeted SRM on TSQ Altis Plus EFOX (triple quadrupole) for routine high-throughput labs; (B) full-scan high-resolution Orbitrap Exploris EFOX at 60,000 FWHM for flexible targeted and retrospective analysis.

Used instrumentation

• Automated DLLME: Thermo Scientific TriPlus RSH SMART Autosampler (automated extraction and centrifugation workflow).
• UHPLC: Thermo Scientific Vanquish Duo UHPLC System (single- or dual-column operation for parallel confirmation runs).
• Columns: Thermo Scientific Hypersil GOLD C18 and Hypersil GOLD C8.
• Mass spectrometers: Thermo Scientific TSQ Altis Plus EFOX Edition (triple quadrupole, SRM) and Thermo Scientific Orbitrap Exploris EFOX Mass Detector (HRMS, full scan at 60,000).
• Software: Chromeleon Chromatography Data System (CDS) v7.3.2 for sequence control, sample prep automation and data processing.

Results and discussion

The automated DLLME workflow provided robust PFAS quantitation across multiple complex matrices with comparable performance to traditional SPE + LC-MS workflows performed by an independent accredited laboratory. Key performance highlights:

• Panel: 61 PFAS selected based on EU and U.S. regulatory lists (including the 40 PFAS in the EU Drinking Water Directive and additional emerging targets such as GenX).
• Sensitivity and linearity: Extracted calibration from 0.1 to 100 ng/L with 5 ppm mass extraction window for HRMS; quantifiable results down to sub-ng/L for several PFAS in tap and groundwater samples.
• Representative findings: Tap water extracts showed seven PFAS quantified between ~0.3 and ~12.7 ng/L depending on instrument; groundwater and soil samples returned higher levels (example soil: PFOS ~531 ng/kg, PFOA ~97 ng/kg, PFHxS ~111 ng/kg). Industrial effluents contained elevated PFAS (e.g., PFBS and PFHxA in the 10^2–10^4 ng/L range for specific effluents).
• Recoveries and comparability: Spiked recoveries generally fell within acceptable ranges (close to 100% for many compounds, with some variation depending on matrix and spike level). Results from DLLME (both direct calibration and standard addition) matched third-party SPE-based analyses closely, demonstrating method accuracy.
• Workflow advantages by detector type: Triple quadrupole SRM provided well-established targeted specificity and ion-ratio confirmation; HRMS full-scan simplified method development, enabled unlimited target lists and retrospective data mining while improving discrimination of true signal vs. interferences.

Practical benefits and applications

• Full automation (extraction, concentration, clean-up) reduces hands-on time and operator variability; walkaway operation supports high-throughput labs.
• Low solvent consumption (~2 mL/sample) and elimination of SPE cartridges/filters reduce cost and environmental footprint.
• Matrix-agnostic protocol: identical extraction workflow for drinking water, groundwater, soil, and industrial effluent increases lab flexibility and simplifies batch planning.
• Regulatory compliance: Both TSQ Altis Plus SRM and Orbitrap HRMS options meet sensitivity/performance requirements cited in EU and U.S. guidance for PFAS monitoring.
• Reduced contamination risk: Minimizing manual transfers and cartridge handling lowers potential for lab-based PFAS contamination.

Future trends and potential uses

• Broader adoption of automated microextraction approaches in routine regulatory and environmental monitoring labs to increase throughput and lower cost per analysis.
• Expansion of HRMS workflows for non-target and suspect screening alongside targeted quantitation, leveraging retrospective data analysis to monitor emerging PFAS.
• Further miniaturization and green chemistry initiatives to reduce solvent volumes and waste generation even further.
• Integration of automated sample prep software and laboratory information management systems (LIMS) to streamline end-to-end workflows and reporting.
• Harmonization of methods and inter-laboratory studies to support regulatory acceptance and standardization across jurisdictions.

Conclusion

Automated tandem DLLME combined with either triple quadrupole SRM or high-resolution full-scan MS provides a fast, flexible, and environmentally conscious solution for multi-matrix PFAS analysis. The method achieves high throughput (54 samples per unattended batch), low solvent consumption, and quantitation comparable to traditional SPE workflows, while offering advantages in automation, versatility, and HRMS-enabled retrospective analysis.

References

1. Thermo Fisher Scientific. Application Brief 003164. Dispersive liquid–liquid microextraction for the automated sample preparation of PFAS in drinking water.
2. Thermo Fisher Scientific. PFAS analysis strategy story – direct injection, DLLME, LC-MS/MS, LC-Orbitrap / GC-Orbitrap (Poster).
3. Thermo Fisher Scientific. Application Note 003992 (Automated tandem DLLME workflow for PFAS analysis) — summary of experimental demonstration and validation results.