Millions of eggs were pulled from supermarket shelves in more than a dozen European countries in late July 2017 – and as far as Hong Kong and South Korea – after it was discovered that some had been contaminated with the insecticide fipronil. On July 20 2017, a notification from Belgian officials via the EU RASFF portal alerted that fipronil had been found in eggs produced by some Dutch farms at concentrations from 0.0031 to 1.2 mg/kg (above the EU MRL). Fipronil is an insecticide intended for professional pest control use to combat infestation of insects such as cockroaches; as well as in veterinary medicine to combat fleas, mites, and ticks on dogs and cats. It is a highly toxic compound and it is not authorised for use as a veterinary medicine, biocide or pesticide around food producing animals. Hence it should never have found its way into a chicken coop.
Fipronil and its metabolite fipronil sulfone in eggs can be determined using LC-MS/MS with electrospray ionisation (ESI) in negative ion mode. However, matrix effects from coeluting co-extractives can impact reproducibility of the method. Therefore suitable sample preparation is needed to achieve a sensitive and robust method. The method validation for the determination of fipronil and fipronil sulfone in eggs using liquid chromatography-tandem quadrupole mass spectrometry will be presented. Discussed results will follow the SANTE criteria (SANTE/11945/2015) set by EC, including a minimum of 5 replicates at the targeted LOQ of the method (0.002 mg/kg) and at least one other higher level (0.02 mg/kg). In this method, the extraction of analytes was performed by modified QuEChERS. For co-extracted lipids removal, simple pass-through solid-phase extraction (SPE) was involved using Oasis PRiME HLB syringe filters. Mean recovery and repeatability (RSDr) for fipronil and fipronil s ulfone was 95 % (1.2 % RSD) and 96 % (1.4 % RSD), respectively. The benefits of this simple and quick sample preparation will be discussed with the method validation results.