Development of Salt-Induced Homogenous Liquid–Liquid Microextraction Based on iso-Propanol/Sodium Sulfate System for Extraction of Some Pesticides in Fruit Juices

In the present work, a simple and fast sample pretreatment method based on salt-induced homogenous liquid–liquid microextraction has been proposed for the extraction and preconcentration of some widely used pesticides (diazinon, ametryn, chlorpyrifos, penconazole, oxadiazon, diniconazole, and fenazaquin) from different fruit juice samples prior to gas chromatography-flame ionization detection. Initially, a small volume (microliter level) of an extraction solvent (iso-propanol) is added into an aqueous phase containing the analytes in order to obtain a homogenous solution. Then, a phase separation agent (sodium sulfate) is added into the homogeneous solution. By this action, the extraction solvent releases from the homogenous solution in the form of tiny droplets containing the analytes and collects on the surface of the aqueous phase as a thin film. A home-made device is used to simplify the removal of the collected organic phase. Finally, an aliquot of the collected organic phase is removed and injected into the separation system for analysis. Under the optimum conditions, limits of detection and quantification were obtained at the ranges of 0.22–0.48 and 0.73–1.7 μg L−1, respectively. The enrichment factors and extraction recoveries of the selected pesticides ranged from 410 to 480 and 82 to 96%, respectively. The relative standard deviations were ≤ 7% for intra- (n = 6) and inter-day (n = 4) precisions at a concentration of 10 μg L−1 of each analyte. Finally, the proposed procedure was successfully applied to the analysis of real samples including apple, sour cherry, peach, grape, and orange juices in order to simultaneously determine the seven aforementioned pesticides. The proposed approach is simple, sensitive, rapid, and requires low solvent consumption, which, in the era of green chemistry, represents a significant advantage. This method and the obtained results can contribute in the improvement of food quality as well as monitoring level of pesticide usage in fruit juices.