In-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids for the determination of benzoylurea insecticides in water and tea beverage samples

A novel in-syringe dispersive liquid-liquid microextraction based on the solidification of ionic liquids (in-syringe SIL-DLLME) was coupled with high-performance liquid chromatography-ultraviolet detector (HPLC-UVD) to detect five benzoylurea insecticides (BUs) in water and tea beverage samples. In this method, the hydrophobic ionic liquid [N₈₈₈₁][PF₆] was formed in situ by the metathesis reaction between [N₈₈₈₁]Cl and the anion-exchange reagent KPF₆ to extract the target analytes. The whole extraction procedure was performed in a syringe. The solidified extractant could be separated from the aqueous phase by exposing the emulsified extraction solution to an ice bath and then easily collected by squeezing out the aqueous phase through the prepared NWPP-based needle. Various parameters affecting the extraction efficiency, such as the amount of [N₈₈₈₁]Cl, the molar ratio of [N₈₈₈₁]Cl to KPF₆, salt addition, cooling time, solution temperature, sample pH and sample volume, were evaluated. Under the optimized conditions, the proposed method was validated with satisfactory results: good linearities with coefficients of determination greater than 0.99 were obtained in the range of 2–500 µg L⁻¹; the limits of detection varied between 0.29 and 0.59 µg L⁻¹; the recoveries of the five benzoylurea insecticides ranged from 85.93% to 90.52%; and the intra-day (n=3) and inter-day (n=3) relative standard deviations were less than 5.36%. Finally, the proposed method was successfully used for the determination of BUs in real water and tea beverage samples.