Determination of Fipronil and its Metabolite Fipronil Sulfone in Eggs by Liquid Chromatography-Tandem Quadrupole Mass Spectrometry Using a Modified QuEChERS Method

Significance of the Topic

Fipronil is a potent insecticide prohibited for use in food-producing poultry. Its inadvertent presence in eggs above regulatory limits poses a serious threat to consumer safety and has triggered widespread recalls. A reliable, sensitive test for fipronil and its major metabolite, fipronil sulfone, is essential for regulatory control and industry due diligence.

Objectives and Study Overview

This study describes the development and validation of a modified QuEChERS extraction coupled with liquid chromatography–tandem quadrupole mass spectrometry (LC-MS/MS) to quantify fipronil and fipronil sulfone in chicken eggs. The method targets compliance with EU maximum residue levels (0.005 mg/kg) and meets SANTE/11945/2015 performance criteria.

Methodology and Instrumentation

Sample Preparation and Cleanup:

• A modified QuEChERS protocol (DisQuE extraction salts) was applied to 5 g of homogenized egg.
• Pass-through cleanup utilized Oasis PRiME HLB cartridges to remove >95% of phospholipids and other co-extractives.

Chromatography and Detection:

• ACQUITY UPLC I-Class with HSS T3 column (2.1 × 100 mm, 1.8 µm) at 40 °C.
• Gradient elution: 2 mM ammonium acetate aqueous phase and acetonitrile, 0.4 mL/min, 8.5 min runtime.
• Xevo TQ-XS triple quadrupole MS with electrospray ionization in MRM mode.
• Key transitions: fipronil m/z 435→330 and 435→250; fipronil sulfone m/z 451→415 and 451→282.
• Data acquisition and processing via MassLynx and TargetLynx software.

Main Results and Discussion

The validated method achieved a limit of quantification of 0.002 mg/kg for both analytes, below the EU MRL. Mean recoveries ranged from 95% to 96% with repeatability (RSDr) under 1.5%. Calibration was linear from 0.0005 to 0.05 mg/kg (r²>0.999), and matrix effects were limited to about 2%. Retention times and ion ratios remained within SANTE tolerances, demonstrating excellent selectivity and robustness.

Benefits and Practical Applications

This approach delivers rapid, cost-effective screening and confirmation of fipronil residues in eggs. The efficient cleanup step reduces matrix suppression, decreases system maintenance, and ensures reliable quantification for both regulatory laboratories and food industry quality control.

Future Trends and Potential Applications

Potential extensions include adaptation of the workflow to other egg products, poultry tissues, and additional pesticide targets. Integration with automated QuEChERS platforms and high-resolution mass spectrometry could further enhance throughput and expand monitoring capabilities. Transferability to other LC-MS/MS systems supports wider adoption in routine surveillance.

Conclusion

The described LC-MS/MS method with modified QuEChERS extraction and Oasis PRiME HLB cleanup satisfies stringent SANTE criteria for fipronil and fipronil sulfone analysis in eggs. It offers high sensitivity, accuracy, and minimal matrix interference, making it suitable for regulatory control and industry due diligence testing.

References

1. Jandova R., McCall E., Ross E., Hird S. Determination of fipronil and fipronil sulfone in eggs by LC-MS/MS using a modified QuEChERS method. Waters Corporation Application Note, 2017.
2. European Commission Regulation (EU) No 1127/2014 amending MRLs for fipronil in food commodities.
3. European Union (2015). SANTE/11945/2015 Guidance Document on Analytical Quality Control and Method Validation Procedures for Pesticide Residues Analysis in Food and Feed.
4. European Union Reference Laboratory for Pesticides in Food of Animal Origin (2017). Analysis of fipronil and metabolites in egg using modified QuEChERS.