Direct injection of drinking water for the analysis of 54 PFAS compounds by LC-MS/MS aligned with current and evolving global regulations

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants linked to adverse health effects. Their widespread use in consumer products and industrial applications leads to ubiquitous exposure through water, dust, and food. Regulatory bodies in Europe and beyond have set stringent limits for PFAS in drinking water, driving the need for sensitive, robust analytical methods.

Objectives and Study Overview

The study aimed to develop and validate a direct-injection LC-MS/MS workflow capable of quantifying 54 PFAS in drinking water at ng/L levels. The method was aligned with current EU and UK drinking water directives, targeting reporting levels as low as 0.1 µg/L for PFAS sums and individual compound limits down to 0.1 ng/L.

Methodology and Instrumentation

The analytical setup included:

• Thermo Scientific Vanquish Flex Binary UHPLC
• Thermo Scientific TSQ Altis Plus triple quadrupole mass spectrometer with HESI source
• Delay column (Acclaim 120 C18, 50×2.1 mm, 2.2 µm) to retain system background PFAS
• Analytical column (Acclaim 120 C18, 150×2.1 mm, 3 µm) at 40 °C
• Strong-solvent loop and user-defined autosampler shake program for homogeneous injection

Sample preparation involved diluting 100 µL of water sample with mobile phase B (methanol with 2 mM ammonium acetate and 0.1% acetic acid), spiking with 19 isotope-labeled internal standards, vortex mixing, and direct injection. Calibration standards ranged from 0.1–100 ng/L in 50:50 water:mobile phase B.

Main Results and Discussion

Key performance metrics:

• Limits of quantification (LOQs): 0.1–5 ng/L, meeting regulatory requirements
• Linearity: correlation coefficients (R²) >0.99 across the calibration range
• Precision: 81% of compounds showed RSD <20% at LOQ level
• Accuracy: 93% of compounds within 80–120% recovery at LOQ
• Recovery in tap and bottled water: 80–130% with RSD <30% for spiking levels of 5, 25, and 75 ng/L
• Blank analyses demonstrated effective mitigation of system and sample contamination via delay column and material selection

The direct-injection approach eliminated solid-phase extraction, reducing labor, consumable use, and potential contamination while maintaining sensitivity.

Benefits and Practical Applications

This workflow offers:

• High throughput through simplified sample preparation and direct injection
• Robust contamination control using delay column and defined autosampler protocols
• Compliance with EU and UK PFAS monitoring guidelines
• Broad analyte coverage from C4 to C20 PFAS, including novel PFAS such as HFPO-DA (GenX) and ADONA
• Integrated data processing and reporting via Chromeleon CDS for streamlined laboratory operations

Future Trends and Applications

Emerging directions include:

• Extension of direct-injection workflows to complex matrices (wastewater, sludge)
• Integration of high-resolution mass spectrometry for non-target PFAS screening
• Automated sample-handling and real-time contamination tracking
• Machine-learning algorithms for chromatographic peak deconvolution and background subtraction
• Continuous expansion of target PFAS lists to cover new regulatory requirements and novel chemistries

Conclusion

The presented direct-injection LC-MS/MS method on the TSQ Altis Plus is a robust, sensitive, and efficient solution for routine monitoring of 54 PFAS in drinking water. It meets stringent European regulatory levels, minimizes sample preparation steps, and enhances laboratory throughput while ensuring data quality.

References

1. Jian JM et al. A short review on human exposure to and tissue distribution of PFAS. Sci Total Environ. 2018;636:1058–1069.
2. Fenton SE et al. PFAS toxicity and human health: current state and future research. Environ Toxicol Chem. 2021;40(3):606–630.
3. Directive (EU) 2020/2184 on quality of water intended for human consumption.
4. French official limits of quantification for water analyses.
5. Requirements for PFAS monitoring by water companies in England and Wales.
6. Belgian methodology for PFAS in water by LC-MS/MS.
7. Italian reference methods for PFAS in drinking water (DL.vo 31/2001).
8. Thermo Fisher Scientific AN 65397: Direct analysis of PFAS in water by LC-MS/MS.
9. Thermo Fisher Scientific TN 74138: Custom injection programs and solvent effects mitigation in LC.