Preparation and Characterization of a Novel Solid-Phase Microextraction Material for Application to the Determination of Pesticides

Abstract

ABSTRACTThe preparation and characterization of a novel solid-phase microextraction fiber is reported with application to the determination of pesticides in fruit juice. The fiber was fabricated by electrochemically coating a stainless steel wire with a thin polymeric film of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) benzenamine. The procedure was initiated in 10 mL of acetonitrile containing 5.5 mg of monomer, 0.1 mol NaClO4, and 0.1 mol LiClO4 by cycling the potential between −0.5 and 1.2 V with a scan rate of 100 mV/sec. The morphology of the fiber surface was examined by scanning electron microscopy and its stability was characterized by thermal gravimetric analysis. The fiber was exposed to headspace extraction of bromopropylate, chlorpyrifos, lambda-cyhalothrin, penconazole, and procymidone prior to the analysis by gas chromatography with an electron capture detector. Operational parameters affecting the extraction efficiency, adsorption and desorption times and temperature, and stirring rate were screened using a Plackett-Burman Design. Emerging parameters were further optimized via Central Composite Design that were 20 min at 64°C for adsorption and 4.4 min at 250°C for desorption. Solution parameters were optimized to be 5.0 mL of sample in pH 2.0 Britton-Robinson buffer containing 0.1 mg/L NaCl to promote the volatilization of the analytes. The limits of detection were at the ng/mL level for the pesticides. The fiber was used as a selective and sensitive tool for the trace determination of these pesticides in grape juice.