Development of an ultrasonic-assisted and effervescent tablet-assisted dispersive liquid-liquid microextraction based on ionic liquids for analysis of benzoylurea insecticides

In this work, an effervescent tablet containing ionic liquids was made and used in ultrasonic-assisted dispersive liquid-liquid microextraction for extraction and preconcentration of benzoylurea insecticides (hexaflumuron, teflubenzuron, triflumuron and chlorfluazuron) in fruit juice and vegetable sample prior to high-performance liquid chromatography-diode array detection. In this method, the effervescent tablet composed of sodium bicarbonate, tartaric acid and potassium bromide is used for dispersion of an extraction solvent into an aqueous phase containing the analytes. An ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is used as the extraction solvent. An acid-base reaction between tartaric acid and sodium bicarbonate is immediately occurred, after releasing the tablet into the aqueous phase, and the produced CO2 leads to dispersion of the extraction solvent (placed in the tablet) into the solution as tiny droplets. Also, sonication is used in the improvement of dispersion of the extraction solvent and mass transfer of the analytes into the tiny droplets of the extraction solvent. Under the optimum conditions, limits of detection and quantification were obtained in the ranges of 0.04-0.19 and 0.13-0.64 ng mL(-1), respectively. The enrichment factors and extraction recoveries of the selected analytes ranged from 370 to 465 and 74% to 93%, respectively. The relative standard deviations were <= 6.9% for intra-day (n = 6) and inter-day (n = 5) precisions at a concentration of 1 ng mL(-1) of each analyte. Finally, some fruit juice and vegetable samples were effectively analysed by the proposed method, and hexaflumuron was found in cabbage sample, at ng g(-1) concentration range.