Thermo Fisher Scientific has produced an application note describing a quick and simple method for the determination of fipronil and fipronil sulfone in eggs using an in-house modified QuEChERS acetonitrile extraction protocol and LC-MS/MS determination.
Introduction
Recently, it was reported that millions of eggs contaminated with the insecticide fipronil have been distributed to more than 17 countries. On July 20th 2017, it was made public that in some cases the pesticide fipronil was mixed with another formulation and sprayed on chickens against ticks, fleas and lice. As the determined levels were in some cases substantially higher (up to 1.2 mg/kg) than the EU MRL of 0.005 mg/kg for the sum of fipronil and fipronil sulfone, there is a demand for quick and efficient methods for the determination of both substances in egg matrix and potentially in chicken meat.
LC-MS/MS Conditions
Thermo Scientific™ UltiMate3000™ RSLC consisting of binary gradient pump, autosampler and thermostated column compartment was connected to a Thermo Scientific™ TSQ Quantis™ triple quadrupole mass spectrometer.
Data evaluation was performed using Thermo Scientific™ TraceFinder™ 4.1 Software.
Results and Discussion
The recovery of the method was tested by analysis of blank egg samples spiked with fipronil and fipronil sulfone each at 0.5, 1 and 5 ng/g (n = 3 at each concentration). The calibration was carried out using matrix matched calibration solutions prepared at 0.1, 0.5, 1, 5, 10, 50, 100 ng/mL (corresponding to 0.2-200 ng/g in eggs) by spiking blank egg extracts with standard solutions prepared in acetonitrile. The chromatographic peak overlay of quantifier and qualifier ions of both fipronil and fipronil sulfone are illustrated in Figure 3 (see application note).
Conclusion
The study demonstrates the suitability of the UltiMate 3000 RSLC TSQ Quantis LC-MS/MS system for the analysis of fipronil and fipronil sulfone in egg extracts. The limit of quantification and identification of 0.0005 mg/kg for each of fipronil and fipronil sulfone is 5x below the EU statutory MRL for the sum of fipronil and fipronil sulfone and the results are in full compliance with the SANTE11945/2015 analytical quality control guidelines for pesticides. Sample preparation, using a modified QuEChERS protocol, takes around 15 min and allows routine high throughput analysis. Using Accucore aQ column technology, the run time could be shortened to 8 min while maintaining excellent separation efficiency and robustness. The study proves very good robustness of the system allowing uninterrupted analysis of up to 100 egg samples without the need for any system maintenance.
