An Optimized Extraction Procedure for Determining Acaricide Residues in Foundation Sheets of Beeswax by Using Gas Chromatography-Mass Spectrometry

Pesticides can be found in beehives for several reasons, including contamination from surrounding cultivars; yet one of the most pertinent is related to the fact that beekeepers employ acaricides to control various types of mites, which may accumulate in beeswax due to their lipophilic nature. In the present study, foundation sheets of different origins, collected over a period of three years, were analyzed to detect the residues of seven acaricides (atrazine, chlorpyrifos, chlorfenvinphos, alpha-endosulfan, bromopropylate, coumaphos, tau-fluvalinate) by gas chromatography with mass spectrometric detection. An efficient sample treatment (recoveries between 90% and 108%) is proposed, involving solvent extraction with 1% acetic acid in acetonitrile mixture followed by dispersive solid-phase extraction (enhanced matrix removal lipid) and a polishing step. An evaluation was made of the analytical performance of the proposed method. It was shown to be selective, linear from a limit of quantification to 5000 µg/kg, precise (relative standard deviation values were below 6%), and with a goo sensitivity (limit of quantification ranging from 5 to 10 µg/kg). Finally, results showed that a large majority of the sheets analyzed (>90%) contained residues of at least one of these compounds. Coumaphos and tau-fluvalinate residues were the most common, with chlorpyrifos and chlorfenvinphos detected to a lesser extent.