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A novel electrospun composite nanofiber-based adsorbent (polyurethane/polystyrene-silica) was fabricated, characterized, and used in the headspace solid-phase microextraction of the acetylated derivatives of chlorophenols in water samples before gas chromatography with micro electron capture detection. The surface morphology, chemical composition, thermal stability, and structure of the fibers were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller and Barrett-Joyner-Halenda techniques. The effect of the main parameters influencing the efficiency of the method including extraction temperature, salt concentration, and extraction time was investigated and the optimized conditions were obtained. The linear dynamic ranges were 0.1-800 ng/mL. The relative standard deviations (n = 3) and the limits of detection were 2.64-9.57% and 0.0234-0.830 ng/mL, respectively. The relative recoveries for real samples (river water and sewage of our university campus) were between 90.8 and 111%.

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A new type of adsorbent composed of magnetic three-dimensional graphene coated with silver nanoparticles was synthesized by an electroless technique and used in the magnetic solid-phase extraction of selected pesticides (fenitrothion, chlorpyrifos, and hexaconazole) before gas chromatography with a micro-electron capture detector. The adsorbent was characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and field-emission scanning electron microscopy. The important extraction parameters such as pH, adsorbent dose, extraction time, and desorption conditions were investigated. Under the optimal conditions, the analytical figures of merit were obtained as: linear dynamic range of 0.1-5 ng/g with determination coefficients of 0.991-0.996; limit of detection of 0.07-0.13 ng/g; limit of quantification of 0.242-0.448 ng/g; and the intraday and interday relative standard deviations (C = 5 ng/g, n = 3) were 3.8-8.7 and 6.6-8.9%, respectively. The developed method was successfully applied for analysis of the selected pesticides in tomato and grape with extraction recoveries in the range of 72.8-109.6%.

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