Combination of QuEChERS extraction with magnetic solid phase extraction followed by dispersive liquid-liquid microextraction as an efficient procedure for the extraction of pesticides from vegetable, fruit, and nectar samples having high content of solids

In this study, a combination of QuEChERS extraction-magnetic solid phase extraction-dispersive liquid-liquid microextraction has been reported for the extraction and preconcentration of different pesticides (diazinon, penconazole, oxadiazon, diniconazole, and fenazaquin) from various vegetable, fruit, and nectar samples followed by gas chromatography-flame ionization detection. The QuEChERS extraction method is used for the extraction of the analytes from the scums of the samples. A few mg of magnetic nanoparticles (Fe3O4@SiO2@ph) are used for the extraction of the analytes dissolved in the juices of the samples. In the following to achieve high enrichment factors a microextraction procedure, dispersive liquid-liquid microextraction, is carried out. The synthesized nanoparticles are characterized by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectrophotometer. Some important parameters which affect the extraction efficiency such as weight of the magnetic sorbent, vortexing time, elution solvent kind and volume, extraction solvent kind and volume, pH, and salt addition are studied. Under the optimum extraction conditions, limits of detection and quantification were obtained in the ranges of 0.21-0.34 and 0.69-1.12 mu g L-1, respectively. The calibration graphs were linear with coefficients of determination >= 0.9930. High enrichment factors (245-351) and good extraction recoveries (49-70%) were obtained. The relative standard deviation was <= 9% for intra- (n = 6) and inter-day (n = 4) precisions.