Dispersive solid phase extraction using zinc oxide graphitic carbon nitride as sorbent followed by dispersive liquid–liquid microextraction for the determination of organochlorine pesticides from fruit juice samples

Abstract

ABSTRACT In the present work, we proposed a novel method; dispersive solid-phase extraction followed by dispersive liquid–liquid microextraction for selective extraction and preconcentration of organochlorine pesticides in fruit juice samples. Parameters affecting the performances of both extraction steps have been rigorously studied and optimized. For the dispersive solid-phase extraction, zinc oxide-graphite carbon nitride was used as a sorbent for the first time. In the extraction, 100 mg of the sorbent was added to an aqueous solution. The content was then vortexed thoroughly to disperse the sorbent into the sample solution and to enhance the transfer of the analytes to the extraction phase (sorbent). The extracted analytes were then desorbed using 500 μL methanol. Subsequently, for the dispersive liquid-liquid microextraction, 50 μL of chloroform (as an extractant) was added to methanol-desorbed analytes and then rapidly injected into 5 mL deionised water. After centrifuging, 35 μL of the sedimented phase was withdrawn into an auto-sampler vial, and then 1 μL was injected into a gas chromatography-mass spectroscopy analysis. Under the optimum conditions, the proposed method showed satisfactory analytical performance characteristics: linearity ranging from 0.1–10.24 µg/L with coefficients of determinations (R2) from 0.9948–0.9995; The limit of detections ranging from 0.004–0.01 µg/L; intra- and inter-day precisions expressed as relative standard deviations ranging from 1.1–7.8%, and extraction recoveries varying from 80.8–109.2%. Generally, the proposed method is selective and efficient for the extraction and preconcentration of the target analytes from fruit juices and related matrices.