Analysis of Per- and Polyfluoroalkyl Substances (PFAS) Using Triple Quadrupole Mass Spectrometer Part 2 -Milk-

Importance of the Topic

Per- and Polyfluoroalkyl Substances PFAS are persistent organofluorine chemicals used in fire retardants nonstick coatings and food packaging. Their stability leads to environmental accumulation and potential food chain transfer. Recent studies document PFAS migration into dairy products raising health concerns. Reliable quantification of PFAS in milk is essential for food safety monitoring and regulatory compliance.

Aims and Study Overview

This study targets quantitative analysis of thirty PFAS defined by AOAC SMPR in whole milk samples. Key objectives include achieving low limits of quantification down to 0.01 µg/kg and validating accuracy and precision across a wide concentration range. Spike recovery experiments assess method performance at 0.01 0.1 and 1 µg/kg levels.

Methodology

Sample preparation follows a modified QuEChERS protocol:

• Weigh 10 g milk add isotopic internal standards ISTDs acetonitrile and formic acid
• Shake with QuEChERS extraction salt centrifuge to separate organic layer
• Perform dispersive SPE with PSA and ENVI-Carb sorbent centrifuge collect supernatant
• Evaporate under nitrogen to near 1 mL adjust to final volume with 90% methanol water
• Vortex centrifuge and transfer to vial for LC-MS/MS analysis

Used Instrumentation

• Shimadzu Nexera X3 UHPLC system
• Shimadzu LCMS-8060NX triple quadrupole mass spectrometer with ESI negative ionization
• Shim-pack Scepter C18 analytical and delay columns
• TurboVap LV nitrogen blowdown evaporator
• Centrifuges and orbital shaker for sample cleanup

Main Results and Discussion

All thirty PFAS eluted within 8 minutes with clear separation from interfering bile acids. Calibration curves prepared in matrix from 0.005 to 1 µg/kg exhibited linearity with coefficients of determination above 0.99 for all compounds. Method performance at three spike levels:

• 0.01 µg/kg: recoveries 92.0–119.6% repeatability ≤15.7%
• 0.1 µg/kg: recoveries 96.6–107.8% repeatability ≤8.1%
• 1 µg/kg: recoveries 93.9–101.7% repeatability ≤4.4%

PFOA PFNA PFHxS and PFOS met AOAC criteria of LOQ ≤0.01 µg/kg recovery 65–135% and repeatability ≤25%. Results confirm robust quantification at trace levels.

Benefits and Practical Applications

• Enables accurate monitoring of PFAS in dairy products to support food safety programs
• Covers a broad range of PFAS including short and long chain homologues
• High throughput analysis with run time under 15 minutes per sample
• Matrix matched calibration and ISTDs ensure reliable quantitation

Future Trends and Potential Applications

Advances may include automated sample preparation workflows and high resolution mass spectrometry for non targeted PFAS screening. Extension of this method to other food matrices and environmental samples will broaden surveillance capabilities. Development of reference materials and harmonized protocols will further improve interlaboratory comparability.

Conclusion

This validated LC-MS/MS method achieves sensitive accurate and reproducible quantification of thirty PFAS in milk. Recovery and precision meet or exceed AOAC requirements. The approach supports routine PFAS monitoring in dairy and can be adapted for broader food safety applications.

References

1. Van Asselt ED et al Transfer of perfluorooctane sulfonic acid PFOS from contaminated feed to dairy milk Food Chemistry 141 2013 1489–1495
2. AOAC SMPR 2023.003 Performance Requirements for Per- and Polyfluoroalkyl Substances PFAS in Foods 2023
3. FDA C-010.03 Determination of 30 Per and Polyfluoroalkyl Substances PFAS in Food and Feed using LC-MS/MS 2020