Determination of Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) in Water with FREESTYLE XANA and LC-MS/MS

Significance of the Topic

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are highly persistent environmental contaminants used for their unique water- and oil-repellent properties in a wide range of consumer and industrial products. Owing to their resistance to degradation, PFAS accumulate in water bodies, wildlife and humans, posing potential health risks such as carcinogenicity, reproductive toxicity and immunosuppression. Growing regulatory demands and lower permissible limits drive the need for reliable, high-throughput analytical methods capable of detecting trace levels of PFAS in water.

Objectives and Study Overview

This study presents a fully automated workflow for the determination of 14 target PFAS in water using solid-phase extraction (SPE) on the FREESTYLE XANA robotic platform, coupled with LC-MS/MS analysis. The method complies with DIN 38407-42 requirements, achieves parallel processing of 24 samples to enhance throughput, and evaluates recovery, background contamination and reproducibility.

Methodology and Instrumentation

Reagents and Standards:

• LC-MS grade water, methanol, acetonitrile, formic acid, ammonium acetate, ammonia.
• Native and mass-labelled PFAS standard solutions (2.0 µg/mL) from Wellington Laboratories.

Sample Preparation:

• Spiking: 500 mL water samples at 10 ng/L analyte level via 25 µL working solution additions.
• Blank procedure: solvent evaporation under N₂, reconstitution in acetonitrile, drying, final volume in 6:4 methanol/water.

Automated SPE System (FREESTYLE XANA):

• Components: FREESTYLE BASIC robotic platform, PFAS-free SPE module, XANA controller, CHROMABOND HR-XAW cartridges.
• System modifications: replacement of fluorocarbon parts with polyethylene/polypropylene to minimize PFAS release.

LC-MS/MS Analysis:

• Instrument: Agilent 1290 Infinity II UPLC coupled to SCIEX API 5500 QqQ in negative ESI mode.
• Chromatography: NUCLEOSHELL® Bluebird RP18 column (2.7 µm), gradient from 20% to 95% methanol with 5 mM ammonium acetate, 0.33 mL/min, 40 °C.
• Detection: scheduled MRM, ion spray −4,500 V, curtain gas 30 psi, 400 °C.

Main Results and Discussion

Recovery and Precision:

• Fourteen PFAS exhibited recoveries between 66% and 113%, with relative standard deviations below 4%.

Background Contamination:

• Comparative analysis of neat solvents and system-processed blanks confirmed negligible PFAS contribution from the automated SPE platform.

Chromatographic Performance:

• Baseline separation of analytes achieved within a 15 min run time; blank matrices showed no interfering peaks at analyte retention times.

Benefits and Practical Applications of the Method

The automated SPE-LC-MS/MS protocol offers:

• High sample throughput through parallel processing of up to 24 samples with minimal user intervention.
• Robust recoveries and low variability, ensuring reliable quantification at sub-ng/L levels.
• Reduced cross-contamination by using PFAS-free system components.

Future Trends and Opportunities

As regulations on PFAS become more stringent, analytical laboratories will require methods with wider analyte panels and lower detection limits. Emerging techniques such as high-resolution mass spectrometry, miniaturized SPE formats and on-line coupling with data analytics platforms will further enhance sensitivity, selectivity and throughput. Automation will remain central to meeting increasing demand for PFAS monitoring in environmental and drinking water matrices.

Conclusion

The described methodology demonstrates a fully automated, DIN-compliant approach for trace PFAS determination in water, combining a PFAS-free SPE platform with sensitive LC-MS/MS detection. It delivers high recoveries, low backgrounds and efficient sample processing, making it a robust solution for routine environmental analysis under evolving regulatory requirements.

References

1. Wollseifen HR, Wierer S. Determination of PFAS in Water with FREESTYLE XANA and LC-MS/MS. Application Note AN0033. LCTech GmbH & MACHEREY-NAGEL; 2019.
2. DIN 38407-42. German Standard Methods for Water Analysis – Determination of Perfluoroalkyl Substances; 2019.
3. Wellington Laboratories. Native and Mass-Labelled PFAS Standard Solutions; 2019.