Automated solid phase extraction and UHPLC-MS/MS analysis of per- and Poly- fluoroalkyl substances in milk

Importance of the Topic

PFAS contamination in food, especially milk, poses significant health risks and is subject to stringent regulatory limits. The study addresses the need for sensitive, reproducible analytical methods to monitor PFAS levels in milk products for consumer safety.

Objectives and Study Overview

This work aims to develop and validate a fully automated solid phase extraction and UHPLC-MS/MS workflow for the determination of 25 PFAS in various milk matrices. The study compares manual and automated protocols, evaluates method performance against EU regulations, and demonstrates practical implementation in routine labs.

Methodology and Instrumentation

Automation is achieved using the Andrew+ Pipetting Robot combined with an Extraction+ Vacuum Manifold under OneLab software control.
Sample cleanup employs Oasis PFAS GCB/WAX SPE cartridges.
Instrumentation details:

• UHPLC System: ACQUITY Premier with PFAS analysis kit
• Columns: ACQUITY Premier BEH C18 2.1 × 50 mm, 1.7 μm; Atlantis Premier BEH C18 AX 2.1 × 50 mm, 5 μm
• Mass Spectrometer: Xevo TQ-Absolute with ESI in negative mode
• Detection: Time-windowed MRM for 25 PFAS species

Key Results and Discussion

Calibration curves achieved coefficients of determination above 0.99, with residuals within ±20% for regulated PFAS and ±35% for others.
LOQ of 0.005 μg/kg was validated for PFOS, PFOA, PFNA, and PFHxS in milk, meeting EU Recommendation 2022/1431.
Recoveries ranged from 98 to 118% for the four priority PFAS, with overall recoveries averaging 102 ± 18% across all levels.
Automated and manual workflows yielded comparable results with minimal background contamination.
Optimization of liquid handling protocols, such as multipoint rinsing of sample tubes, enhanced analyte recovery and reproducibility.

Benefits and Practical Applications

• Reduction of hands-on time by approximately 88 minutes for calibration preparation and 2 hours for extraction of 12 samples
• Improved reproducibility and minimized analyst variability
• Compliance with EU maximum levels and method performance criteria
• Streamlined adoption using downloadable OneLab automation protocols

Future Trends and Possibilities

Anticipated advances include integration of fully automated end-to-end PFAS workflows, expansion of target lists to emerging PFAS compounds, and application of artificial intelligence for method optimization and laboratory scheduling.

Conclusion

The validated automated SPE and UHPLC-MS/MS method provides a robust, high-throughput solution for PFAS analysis in milk, aligning with regulatory requirements and delivering significant time savings and reproducibility improvements in routine testing.

Reference

1. Commission Regulation (EU) 2022/2388 on maximum levels of perfluoroalkyl substances in certain foodstuffs, L 316/38, 8 December 2022.
2. Commission Recommendation (EU) 2022/1431 on the monitoring of perfluoroalkyl substances in food, L 221/105, 26 August 2022.
3. Ng D, Devakishen M, Kuah KX, Adams S, Hird S, Ho J. Automated SPE Analysis of PFAS in Milk. Application Note 720008740, Waters.
4. EURL for halogenated POPs in feed and food: Guidance Document on Analytical Parameters for the Determination of Per- and Polyfluoroalkyl Substances (PFAS) in Feed and Food, May 2022.
5. OneLab Software Protocol for automation of PFAS samples in milk matrices using SPE. Andrew Alliance.
6. Dreolin N, Foddy H, Organtini K, Adams S, Rosnack K, Hancock P. Best practices for monitoring PFAS contamination in a routine shared-space. White Paper 720007905.