Screening and quantitation of perfluoroalkyl and polyfluoroalkyl substances (PFAS) residues in foods using LC-MS/MS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are a class of highly stable chemicals used in numerous industrial and consumer applications. Their resistance to degradation leads to widespread environmental distribution and bioaccumulation in food chains, posing risks to human health, including reproductive and immune system impacts. Monitoring PFAS residues in food commodities such as fish and eggs is crucial for safeguarding public health and ensuring compliance with stringent regulatory limits.

Objectives and Study Overview

This work demonstrates a sensitive and selective liquid chromatography–tandem mass spectrometry (LC-MS/MS) workflow for screening and quantitation of 24 PFAS compounds in fresh fish tissue and egg matrices. The method employs a Thermo Scientific™ TSQ Quantis™ Plus triple quadrupole mass spectrometer and follows SANTE 2021 V2 guidelines and EU Regulation 2022/2388 for method performance. The goal is to achieve trace-level quantitation (≤0.1 µg/kg) in compliance with EU maximum residue limits.

Methodology and Instrumentation

A modified QuEChERS protocol was applied to minimize matrix effects and concentrate analytes:

• Homogenization of fish (3 g) or mixed egg samples.
• Extraction with acetonitrile and citrate-buffered salts (MgSO4, NaCl, citrate) followed by dispersive SPE cleanup (PSA, C18, graphitized carbon black).
• Evaporation under nitrogen and reconstitution in methanol:water (50:50).

Instrumentation Used

UHPLC system:

• Thermo Scientific™ Vanquish™ Flex UHPLC with Quaternary Pump F and Split Sampler FT.
• Accucore™ C18 analytical column (100 × 2.1 mm, 2.6 µm) and Hypersil GOLD C18 delay column (50 × 2.1 mm, 1.9 µm) to reduce isobaric interferences.
• Mobile phases: 2 mM ammonium acetate in water (A) and in methanol (B) with a 20 min gradient at 0.3 mL/min.

Mass spectrometer:

• Thermo Scientific™ TSQ Quantis™ Plus with heated electrospray ionization in negative mode (H-ESI).
• Time-segmented SRM acquisition with two transitions per analyte (one for PFBA and PFPeA) and defined collision energies.
• Optimized ion source parameters: spray voltage –1,500 V, sheath gas 50 Arb, auxiliary gas 10 Arb, vaporizer 300 °C.

Main Results and Discussion

Chromatographic separation effectively resolved branched and linear PFAS isomers and eliminated matrix interferences by using PEEK tubing and a delay column. Method performance highlights:

• Linearity over 0.05–5 ng/mL with R² ≥ 0.99.
• Limit of quantitation: 0.1 µg/kg for all target analytes with signal-to-noise ≥ 10.
• Recovery ranged 70–120% and precision (RSD) < 20% for most compounds; a few analytes exhibited recoveries outside this range but met precision criteria.
• Repeatability across 22 injections of spiked fish tissue (0.2 µg/kg) showed RSD < 10% for representative PFAS (PFOS, PFOA, PFNA, PFHxS).

Benefits and Practical Applications

This workflow offers a robust, high-throughput solution for regulatory monitoring of PFAS in food. Key advantages include:

• Compliance with EU SANTE and MRL requirements.
• Minimal PFAS background contamination via PTFE-free components.
• Capability to distinguish isomeric forms and quantify trace levels in complex matrices.

Future Trends and Applications

Potential extensions of this methodology include:

• Automation of sample preparation and on-line SPE coupling.
• Expansion to other food matrices and environmental samples.
• Integration with high-resolution mass spectrometry for non-target screening.
• Application of data analytics and machine learning for pattern recognition in PFAS profiles.

Conclusion

The optimized LC-MS/MS method using TSQ Quantis™ Plus delivers sensitive, selective, and reproducible quantitation of multiple PFAS at regulatory levels in fish and egg matrices. The approach mitigates contamination risks, achieves stringent performance criteria, and supports routine laboratory workflows for food safety control.

Reference

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