Application of ZIF-67 coated by N-doped carbon dots in dispersive solid phase extraction of several pesticides from fruit juices and its combination with dispersive liquid-liquid microextraction followed by GC-FID

A dispersive solid phase extraction procedure was established for the extraction of some pesticides from fruit juices and then it was combined with dispersive liquid-liquid microextraction for more enrichment of the analytes. For this purpose, 40 mg of zeolitic imidazolate framework-carbon dot composite was dispersed into the sample solution as the sorbent via vortex agitation. After that, the sorbent was collected by centrifugation and the supernatant was wasted. Then, 1 mL of a water-soluble organic solvent (acetone) was added onto the sorbent as the elution solvent. After desorption of the analytes from the sorbent surface, the eluate was mixed with a waterimmiscible organic solvent (1,1,2-trichloro-1,2,2 trifluoroethane) at mu L-level (45 mu L) and the mixture was quickly injected into 5 mL deionized water. The resulting cloudy mixture was centrifuged and 1 mu L of the sedimented phase was injected into a gas chromatography-flame ionization detection system. After the optimization of the method, its validation was evaluated. The data showed that the limits of detection and quantification obtained by this method were in the ranges of 0.22-0.72 and 0.73-2.40 ng mL-1, respectively. The plotted calibration curves were linear in the range of 0.73-1000 mu g L-1 for all analytes. High enrichment factors (375-445), and extraction recoveries (75-89%), and negligible matrices effect were obtained for the investigated analytes by the introduced method. Also, the obtained data showed that all samples were free of the analytes.

Automated summary

A dispersive solid phase extraction procedure combined with dispersive liquid-liquid microextraction was developed for the extraction and enrichment of pesticides from fruit juices. Zeolitic imidazolate framework-carbon dot composite was used as the sorbent, and acetone was used as the elution solvent. The method showed satisfactory limits of detection and quantification, linear calibration curves, high enrichment factors, and extraction recoveries, and negligible matrices effect. All samples were found to be free of the analytes.