Studies On The Methods For Determination Of Multi-organophosphate Pesticide Residues Based On Molecular Imprinting Technology

Organicphosphorus pesticide has been widely used in the production of crops planting due to its advantage of high insecticidal efficiency and low price. But the pesticide residues bring a serious threat to the health of consumers and a negative impact on China’s export trade of agricultural products. Therefore, establishing a fast, accurate and reliable method for determination of organicphosphorus pesticide residues to protect the health of people is very necessary.1. MIMSPD-GC for simultaneous determination of nine organophosphate pesticides residues This paper reports a molecularly imprinted polymer (MIP) prepared using4-(dimethoxyphosphorothioylamino) butanoic acid as the template, acrylamide as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. The novel imprinted polymer was characterized by static and kinetic adsorption experiments, it exhibited good recognition ability and fast adsorption-desorption dynamicd toward trichlorfon, malathion, acephate, methamidophos, omethoate, dimethoate, phosphamidon, monocrotophos, and methyl parathion. Using this imprinted polymer as sorbent, matrix solid-phase dispersion coupled to gas chromatography for simultaneous determination of nine trace organophosphorus pesticide residues was first presented. Under the optimized conditions, the LOD (S/N=3) of this method for the nine organophosphorus was0.3μg kg-1-1.6μg kg-1. The peak area precision [Relative standard deviation (RSD)] for three replicate extractions were ranged from1.2to4.8%. The apple and pear samples spiked with nine organophosphate pesticides at levels of20μg kg-1and100μg kg-1were determined according to this method with good recoveries ranging from81.2to104.7%. Moreover, this developed method was successfully applied to the quantitative detection of the nine organophosphorus pesticide residues in orange samples. 2. MISPE-HPLC for the determination of trichlorfon and monocrotophos residuesThis study reports a new method of molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography (MISPE-HPLC) for simultaneous determination of two organophosphate pesticides residues. Two types of molecularly imprinted polymers (MIPs) were prepared using the trichlorfon and monocrotophos as the template molecule, respectively, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The recognition ability and adsorption-desorption dynamic of each imprinted polymer toward the trichlorfon or monocrotophos were characterised. Using the mixture of trichlorfon-MIP and monocrotophos-MIP (20:80, wt/wt) as solid-phase extraction sorbent, the factors affecting the pre-concentration on the analytes and the sensitivity of the MISPE-HPLC method were optimised. Under optimal condition, the linear range was0.005-1mg L-1. The limit of detection was4.2ng g-1for trichlorfon, and1.2ng g-1for monocrotophos. The peak area precision [Relative standard deviation (RSD)] for three replicates were ranged from2.9to4.5%. The blank rape and cauliflower samples spiked with trichlorfon and monocrotophos at50μg kg-1and5μg kg-1levels were extracted and determined by this method with recoveries ranging from88.5%to94.2%.