Ionic liquid-modified luffa sponge fibers for dispersive solid-phase extraction of benzoylurea insecticides from water and tea beverage samples

In the present study, a convenient, low-cost, sensitive and environmentally friendly method for the determination of four benzoylurea insecticides (BUs) in water and tea beverage samples was developed. The alkalized luffa sponge fibers (AL) were modified by the ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C₁₆MIM]Br) through physisorption and used as the sorbent of dispersive solid-phase extraction (DSPE). The sorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The retained analytes were eluted using 200 μL of methanol and then quantified by high performance liquid chromatography-ultraviolet detection (HPLC-UVD). The influences of extraction parameters of [C₁₆MIM]Br-AL-DSPE on the BUs were thoroughly studied. Under the optimal conditions, good linearity was observed over the concentration range of 1-500 ng mL^-1, with coefficients of determination greater than 0.99. The limits of detection (LODs) of the developed method were 0.14-0.21 ng mL^-1 in water and 0.19-0.23 ng mL^-1 in tea beverage samples. Satisfactory recoveries were achieved in the range of 72.8-89.3%, with relative standard deviations lower than 10%. Finally, the established [C₁₆MIM]Br-AL-DSPE-HPLC-UVD method was successfully applied for the determination of BU residues in environmental water and tea beverage samples.