Combination of poly (ε-caprolactone) grafted graphene quantum dots-based dispersive solid phase extraction followed by dispersive liquid-liquid microextraction for extraction of some pesticides from fruit juices prior to their quantification by gas chromatography

In this study, a poly (epsilon-caprolactone) grafted graphene quantum dots-based dispersive solid phase extraction coupled with dispersive liquid-liquid microextraction has been developed to extract nine pesticides including penconazole, chlorpyrifos, haloxyfop-R-methyl, oxadiazon, clodinafop-propargyl, diniconazole, fenazaquin, fenpropathrin, and fenoxaprop-P-ethyl from different packed fruit juice samples (pomegranate, watermelon, apricot, grape, sour cherry, apple, and orange juices). In the first step, the analytes are adsorbed onto the sorbent and after that the sorbent is settled down by centrifugation and eluted with an appropriate elution solvent (methanol). In the second step, the obtained eluant is mixed with an appropriate preconcentration solvent (1,1,2-TCE) at mu L-level and the mixture is spread into deionized water. After centrifugation, a fraction of the sedimented phase is removed with a microsyringe and injected into the separation system for analysis. The properties of the sorbent were characterized using various techniques including X-ray diffraction, Fourier transform infrared spectrophotometry, scanning electron microscope, Brunauer-Emmett-Teller nitrogen sorption, and differential scanning calorimetry. Under the optimum conditions, the method indicated low limits of detection (0.32-0.76 ng mL(-1)) and quantification (1.1-2.6 ng mL(-1)), high enrichment factors (680-840 and 340-420 for deionized water and fruit juices, respectively), acceptable extraction recoveries (68-84%), and satisfactory relative standard deviations ( <= 8.4% for intra- and inter-day precisions at a concentration of 10 ng mL(-1) of each analyte).