Determination of per- and polyfluorinated alkyl substances (PFAS) in drinking water using automated solid-phase extraction and LC-MS/MS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are a class of persistent, water-soluble chemicals widely used in industrial and consumer applications. Because of their chemical stability and bioaccumulative potential, PFAS have been detected in drinking water sources worldwide and are associated with adverse health effects. Reliable and sensitive analytical methods are therefore critical to monitor PFAS at sub-nanogram per liter levels and to comply with regulatory guidelines such as U.S. EPA Method 537.1.

Goals and Study Overview

This study aimed to develop and validate an automated solid-phase extraction (SPE) workflow coupled to LC-MS/MS for the quantitation of 18 PFAS in drinking water according to U.S. EPA Method 537.1. Key objectives included reducing system background levels, ensuring reproducible recoveries, and achieving low reporting limits through the Thermo Scientific™ Dionex™ AutoTrace™ 280 PFAS extraction system and a Vanquish™ Flex Duo UHPLC-TSQ Fortis™ MS-based detection.

Methodology and Instrumentation

Sample Preparation and Automated SPE

• Sample volume: 250 mL drinking water preserved with Trizma.
• Surrogate standard addition prior to extraction; internal standards added post-extraction.
• AutoTrace 280 PFAS system modified to remove Teflon™ components and equipped with PFAS-safe tubing.
• Three SPE methods programmed: cartridge conditioning and loading, sample elution, and sample-path cleaning (methanol and water).
• Eluent evaporated to dryness under nitrogen at 55–60 °C and reconstituted to 1 mL in 96:4 MeOH/water.

Liquid Chromatography

• UHPLC: Vanquish Flex Duo with PFAS-free kit and Hypersil™ BDS C18 isolator column (2.1 × 50 mm, 5 µm).
• Analytical column: Accucore™ RP-MS (2.1 × 100 mm, 2.6 µm) at 45 °C.
• Mobile phases: A=water + 0.1% acetic acid; B=MeOH + 0.1% acetic acid; C=20 mM ammonium acetate.
• Gradient from 30% B/5% C to 95% B over 14 min; flow rate 0.5 mL/min; injection 5 µL.

Mass Spectrometry

• TSQ Fortis triple quadrupole with H-ESI in negative ion mode.
• Sheath gas 50, auxiliary gas 10, vaporizer 300 °C, ion transfer tube 325 °C.
• Selected reaction monitoring transitions optimized for all 18 analytes and corresponding labeled standards.

Main Results and Discussion

Calibration curves displayed excellent linearity (r2 > 0.99) over 0.1–100 µg/L with forced-zero regression. Chromatographic peak asymmetry factors ranged from 0.8 to 1.2, and all analytes were separated within 15 min. System background was minimized by routine sample-path cleaning and use of PFAS-safe materials. Calculated lowest concentration minimum reporting levels (LCMRLs) ranged from 0.20 to 3.5 ng/L, and method detection limits (MDLs) were between 0.30 and 2.5 ng/L, meeting or exceeding EPA requirements. Precision and accuracy assessments at fortified levels of 16 and 80 ng/L yielded recoveries of 84–123% with relative standard deviations below 10%, demonstrating method robustness.

Benefits and Practical Applications of the Method

The automated SPE workflow significantly reduces hands-on time and operator variability compared to manual vacuum manifold extraction. Controlled flow rates and PFAS-inert components ensure consistent recoveries and low contamination risk. The method is suitable for high-throughput laboratories performing routine drinking water analysis, compliance monitoring, and research on PFAS occurrence.

Future Trends and Potential Applications

Advancements may include online SPE coupling for fully automated sample-to-report workflows, expansion of target analyte panels to emerging PFAS, and integration with high-resolution mass spectrometry for non-target screening. Further miniaturization, enhanced sensitivity at sub-ng/L levels, and adaptation to complex matrices (e.g., wastewater, human serum) will broaden the method’s applicability.

Conclusion

The AutoTrace 280 PFAS automated extraction combined with Vanquish Flex Duo UHPLC and TSQ Fortis MS provides a reliable, sensitive, and high-throughput method for the determination of 18 PFAS in drinking water according to U.S. EPA Method 537.1. The workflow achieves low background, excellent precision, and detection limits suitable for regulatory compliance and environmental monitoring.

Instrumentation Used

• Dionex AutoTrace 280 PFAS SPE System
• Vanquish Flex Duo UHPLC with PFAS-free kit
• TSQ Fortis Triple Quadrupole Mass Spectrometer
• Organomation 12-position N-EVAP Nitrogen Evaporator
• Accucore RP-MS Column, 2.1×100 mm, 2.6 µm
• Hypersil BDS C18 Isolator Column, 2.1×50 mm, 5 µm
• SDVB SPE Cartridges (0.5 g, 6 mL)

Reference

1. U.S. EPA. Basic Information about Per- and Polyfluoroalkyl Substances (PFAS).
2. National Institutes of Health, NIEHS. Polyfluoroalkyl Substances (PFAS).
3. U.S. EPA. Drinking Water Health Advisories for PFOA and PFOS.
4. U.S. EPA. Method 537.1: Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by SPE and LC/MS/MS, Version 1.0, November 2018.