A rapid and simple pretreatment method for benzoylurea insecticides in honey samples using in-syringe dispersive liquid–liquid microextraction based on the direct solidification of ionic liquids

A pretreatment method using in-syringe dispersive liquid–liquid microextraction based on the direct solidification of ionic liquids before high performance liquid chromatography analysis was developed for the determination of benzoylurea insecticides (BUs) in honey samples. The hydrophobic ionic liquid [N₄₄₄₄][PF₆], formed in situ by the hydrophilic ionic liquid [N₄₄₄₄]Cl and the ion exchange reagent KPF₆, was used to extract the target analytes. The entire extraction procedure was performed in a syringe. The extractant was solidified at room temperature and collected using a nylon membrane filter. This technique did not require a dispersive solvent, vortex mixer, ultrasound bath, or centrifugation. The parameters affecting the extraction efficiency were investigated through an experimental design. Under the optimal conditions, the limits of detection for the four BUs varied from 0.21 to 0.42 μg L⁻¹ in solution (2.1–4.2 μg kg⁻¹ in honey). Good linearities were obtained in the range of 2–300 μg L⁻¹, with coefficients of determination greater than 0.999. The recoveries of the four BUs ranged from 80.94% to 84.59%. The intra-day (n = 3) and inter-day (n = 3) relative standard deviations were less than 5.08%. Finally, the proposed method was applied to the determination of BUs in commercial honey samples with satisfactory results.