A Poly (3,4-ethylenedioxothiophene) (PEDOT)/UiO-66 composite was electrodeposited on an etched stainless-steel wire as head-space solid-phase microextraction (HS-SPME) coating. A robust, well controlled thickness, and uniform coating of metal organic framework composites can be realized by the electrodeposited strategy. The incorporated UiO-66 not only enhanced the uniformity and stability of the composite coating, but also effectively decreased the stacking phenomenon of PEDOT and improved its extraction efficiency, which was over 100 times higher than that of the PEDOT coating without UiO-66. The composite coating was used to enrich seven types of volatile organic compounds (VOCs) in ion-exchange resins, including methyl cyclohexane, benzene, toluene, ortho-xylene, styrene, para-xylene and divinyl-benzene. The results of adsorption isotherm analysis showed that π stacking effect played dominant role between the composite coating and VOCs in the extraction process. The composite coating was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared and thermogravimetric analysis, respectively. A determination method for seven kinds of VOCs was established by HS-SPME coupled with gas chromatography-flame ionization detection (GC-FID). Under the optimal experimental conditions, the detection linear range (LRs) was 0.09-100 ng mL −1 , and the detection limit (LODs) was 0.03-0.06 ng mL −1 (S/N = 3). The method was applied for the migration detection of VOCs in four types of ion-exchange resin, which showed satisfactory recovery (84.5-117.2%).
Mohammad Nazari Kalojeh,Roghayeh Hassanpour Sabet,Mir Ali Farajzadeh,Mohammad Reza Afshar Mogaddam,Elnaz Marzi Khosrowshahi,Mustafa Tuzen
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 water-immiscible organic solvent (1,1,2-trichloro-1,2,2 trifluoroethane) at µL-level (45 µL) and the mixture was quickly injected into 5 mL deionized water. The resulting cloudy mixture was centrifuged and 1 µL 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 µg 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.
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