Determination of fipronil residues in honey and pollen by gas chromatography

This work describes the development of the analytical methodology for determining fipronil residues in honey and pollen samples by gas chromatography with two detecting systems: electron-capture detection (GC-ECD) and mass spectrometry (GC-MS). Fipronil was extracted from honey samples by solid-phase extraction, using alumina as adsorbent and hexane-ethyl acetate (1:1, v/v) as eluting solvent, and from pollen samples by matrix solid-phase dispersion with C18 and acetonitrile, assisted by sonication. The developed methods gave recovery results >90% with relative standard deviations <6% in both matrices. The determination of residue levels was carried out with matrix matched calibration standards, to counteract the matrix effect observed, and heptachlor as internal standard. The limits of detection obtained with GC-ECD were 1 microg/kg for pollen and 0.5 microg/kg for honey and the corresponding values for GC-MS were 0.2 and 0.1 microg/kg, respectively. These methods were applied to the determination of fipronil levels in various samples of honey and pollen commercialised in Spain and no residues of this compound were detected.