Rapid analysis of fipronil and fipronil sulfone in eggs by liquid chromatography and triple quadrupole mass spectrometry

Importance of the Topic

Egg contamination with the insecticide fipronil poses significant public health and regulatory challenges worldwide. The recent distribution of eggs containing fipronil at levels far exceeding maximum residue limits highlights the need for rapid, sensitive and robust analytical methods for routine monitoring in food matrices.

Study Objectives and Overview

This study aimed to develop a fast and straightforward method for quantifying fipronil and its sulfone metabolite in egg samples. The approach integrates a modified QuEChERS acetonitrile extraction protocol with LC-MS/MS analysis on a triple quadrupole system.

Methodology and Instrumentation

• Sample Preparation:
  • Homogenize 5 g egg sample, add 5 mL water and 10 mL acetonitrile, shake and salt out with MgSO4/NaCl.
  • Perform dispersive SPE cleanup using MgSO4 and C18 sorbents.
  • Collect extract for LC-MS/MS injection.
• Chromatographic Conditions:
  • Column: Accucore aQ 100 × 2.1 mm, 2.6 µm at 40 °C.
  • Mobile phase: water (A) and methanol (B) gradient over 8 minutes.
  • Injection volume: 1 µL.
• Mass Spectrometry:
  • TSQ Quantis triple quadrupole with heated electrospray in negative mode.
  • SRM transitions optimized for precursor and three product ions per compound.

Used Instrumentation

• UltiMate 3000 RSLC binary pump and autosampler.
• Thermo Scientific Accucore aQ column.
• TSQ Quantis triple quadrupole mass spectrometer with H-ESI source.
• TraceFinder 4.1 software for data processing.

Results and Discussion

The method achieved recoveries between 89 and 104% for fipronil and 95 to 102% for fipronil sulfone at spike levels of 0.5–5 ng/g. The limit of quantification was 0.5 ng/g (repeatability < 20% RSD), with an estimated detection limit of 0.1 ng/g (S/N > 3). Ion ratio stability remained below 10% RSD. System robustness was confirmed by stable signal responses over 100 consecutive injections without maintenance.

Benefits and Practical Applications

• Quantification limits five times lower than the EU maximum residue level (0.005 mg/kg).
• Compliance with SANTE/11945/2015 analytical quality control guidelines.
• Rapid sample preparation (~15 minutes) suitable for high throughput analysis.
• Short 8-minute run time enhances laboratory productivity.

Future Trends and Applications

Emerging directions include extension of the method to other food matrices such as chicken meat, integration with automated sample handling, and further miniaturization to reduce solvent use and increase throughput. Advances in high-resolution MS may offer additional specificity and multiplexing capabilities.

Conclusion

The validated LC-MS/MS workflow provides a fast, sensitive, and reliable solution for routine monitoring of fipronil and fipronil sulfone residues in eggs, meeting regulatory requirements and supporting food safety control.

References

• Sales S, Mohring S, Godula M. Rapid analysis of fipronil and fipronil sulfone in eggs by LC-MS/MS. Thermo Fisher Scientific Application Brief 72483; 2017.
• Commission Regulation (EU) No 1127/2014 amending MRLs for fipronil.
• European Commission SANTE/11945/2015 guidelines on analytical quality control.
• RASFF Notification 2017.1065 on fipronil contamination in eggs.