Analytical method for the detection of prohibited substances in medicinal biopreparations used in beehives

A method was developed for the determination of flumethrin pesticide in medicinal biopreparations used in beehives. Essential oils (EOs) represent natural, biodegradable alternatives to synthetic pesticides, serving as effective bioacaricides and active pharmaceutical ingredients that prevent or treat infestations without leaving harmful residues in hives. The method combines liquid-solid extraction with gas chromatography with electron-capture detection (GC-ECD) and liquid chromatography with tandem mass spectrometry (LC-MS/MS). For optimization of the extraction process, a model sample in the form of a wooden spatula was soaked by EOs, both individual (coriander, thyme, wormwood and mint) and a mixture of EOs for 15 min. The optimal time of flumethrin absorption on the spatula was set at 80 min. The process of simple sample preparation entails the extraction of medicinal preparations by means of methanol, with the assistance of ultrasound for a duration of 20 min. The method was validated. The obtained limits of quantification for flumethrin determined in model samples were obtained at 0.5 ng/µL for GC-ECD and 0.12 ng/µL for LC-MS/MS, corresponding to 3.57 and 0.86 ng/mg of the sampler, respectively. The recovery of flumethrin was 104.2% with relative standard deviations of 11%. The use of matrix standards for calibration purposes to minimize the matrix effects was proposed. Positive findings in medicinal preparations were reported. The results show that the method is suitable for screening the flumethrin in medicinal biopreparations inserted into a beehive to reveal the contamination of biopreparations or their intentional fraud.