Combination of Modified QuEChERS Extraction Method and Dispersive Liquid–Liquid Microextraction as an Efficient Sample Preparation Approach for Extraction and Preconcentration of Pesticides from Fruit and Vegetable Samples

Abstract

In this study, a combination of modified quick easy cheap effective rugged and safe extraction and dispersive liquid–liquid microextraction has been proposed for the extraction and preconcentration of some widely used pesticides (diazinon, chlorpyrifos, penconazole, oxadiazon, and diniconazole) from fruit and vegetable samples prior to their determination by gas chromatography–flame ionization detection. In the proposed method, firstly, an aliquot of sample is crushed and then its refuse and juice are separated by centrifuging. The juice is transferred to a conical glass test tube. Then acetonitrile as an extraction/disperser solvent is added into the tube containing the refuse. The analyte residues are extracted into acetonitrile after vortexing. The obtained acetonitrile is mixed with an extraction solvent (1,2–dibromoethane) at microliter level and rapidly injected into the juice. As a result, a cloudy state is formed, and the tiny droplets of the extractant containing the extracted analytes are sedimented at the bottom of the tube after centrifugation. Finally, an aliquot of the sedimented organic phase is removed and injected into the separation system for the quantitative analysis. In this study, several significant factors affecting the performance of the introduced method were investigated and optimized. Under the optimum experimental conditions, enrichment factors ranged from 240 to 375 for apricot nectar and 96–150 for solid samples. The relative standard deviations were ≤ 7% for intra-(n = 6) and inter-day (n = 4) precisions at a concentration of 100 μg L−1 of each analyte. Limits of detection were in the ranges of 0.27–0.48 μg L−1 in the solution and 0.68–1.2 μg kg−1 in the solid samples. Finally, several fruit and vegetable samples were analyzed by the proposed method, and penconazole was found in grape at μg kg−1 level.