Determination Of Multi-organophosphate Pesticide Residues Through Gas Chromatography Coupled With Magnetic Separation And Electrochemical Sensor Based On Imprinted Sol-gel

Organophosphate pesticides(OPs) are readily absorbed through the skin and respiratory tract. Their toxicity and potential carnogenicity give rise to a serious public problem. So, the development of a convenient, rapid, reliable and low–cost method for detecting trace levels of OPs is desirable. In this study, two methods for determination of organophosphate pesticide multi–residues of gas chromatography coupled with magnetic solid–phase extraction(MSPE–GC) and electrochemical sensor via magnetic separation, sol–gel and molecularly imprinted technology had been developed.1. MSPE–GC method for the determination of ten organophosphate pesticide residues in fruits.In this study, a γ–Fe2O3/chitosan magnetic microsphere was synthesized and evaluated by the X–ray diffraction(XRD), scanning electron microscopy(SEM) and thermogravimetric analysis(TGA). Results showed that the magnetic microsphere exhibited good adsorption ability and offered fast kinetics for the adsorption of ten OPs. Based on magnetic separation, a simple method of magnetic solid–phase extraction coupled to gas chromatography(MSPE–GC) for simultaneous determination of trace ten organophosphate pesticide residues was developed. Under the optimal conditions, the enrichment factor for ten organophosphate pesticides was 10.1 to 364.7, and the linear range was all 0.001–10.0 mg L-1. The LOD(S/N=3) of the method for the ten pesticides was 0.31 μg kg-1 to 3.59 μg kg-1. The RSD for three replicate extractions of spiked samples was between 2.5% to 6.3%. The pear and apple samples spiked with ten organophosphorus pesticides at 20 and 200 μg kg-1 levels were extracted and determined by this method with good recoveries ranging from 79.9% to 98.7%. Moreover, the method has been successfully applied for the determination of the ten organophosphorus pesticide residues in peach samples.2. Molecularly imprinted electrochemical sensor for detecting acephate and trichlorfon in vegetables.In this study, we developed a novel biomimetic electrochemical sensor sensitized with Fe3O4@carboxyl-functionalized multiwalled carbon nanotubes/chitosan nanocomposite layer using molecularly imprinted film as recognition element for the rapid detection of acephate and trichlorfon. The performance of the imprinted sensor was investigated using cyclic voltammetry(CV) and differential pulse voltammetry(DPV), and results indicated that the sensor exhibited fast responses to both acephate and trichlorfon. The imprinted sensor had good linear current responses to acephate and trichlorfon concentrations in the ranges from 1.0×10-4 to 1.0×10-10 mol L-1 and 1.0×10-5 to 1.0×10-11 mol L-1, respectively. Under optimal conditions, the imprinted sensor had low limits of detection(signal to noise, S/N=3) of 6.81×10-11 mol L-1 for acephate and 8.94×10-12 mol L-1 for trichlorfon. The developed method was successfully applied to detect the acephate and trichlorfon spiked in the fortified kidney bean and cucumber samples with good recoveries ranging from 85.7% to 94.9% and relative standard deviations of 3.46%~5.18%.