Liquid-liquid Extraction Followed by Solid-phase Extraction for the Determination of Lipophilic Pesticides in Beeswax by Gas Chromatography-electron-capture Detection and Matrix-matched Calibration

Analytical methods for the simultaneous analysis of lindane, chlorpyriphos, z-chlorfenvinphos, endosulfan A and B, 4,4'-DDE, 4,4'-TDE, acrinathrine, bromopropylate, tetradifon, coumaphos and fluvalinate in pure beeswax samples are studied. For the analysis of bleached beeswaxes, a liquid-liquid extraction with acetonitrile followed by a clean-up on polymeric cartridges is the best option in terms of recovery and precision. However, some interferences that hinder the identification and quantification of important varroacides are found when non-bleached beeswaxes are analyzed. The analysis of all compounds in the latter samples require a clean-up by coupling an ODS cartridge before the polymeric cartridge. Considerations about the influence of the matrix in the quantitative analysis by a classical external standard calibration are also made and the use of a matrix-matched calibration is advised. Recoveries resulted to be about 100% with coefficients of variation between 10% and 20% (n = 5) for concentrations of 0.5 and 5 mg/kg.