Research For Determination Of Dimethoate And Cephalexin Using Molecularly Imprinted Techniques

In recent years, environmental pollution and food safety problem have increasingly become the focus of attention. The pesticides and antibiotics detection is a hotspot in the field of food safety and environmental protection at home and abroad. Dimethoate and cephalexin, as commonly used sulfur-containing organophosphate pesticide and beta lactam antibiotic seperately, can be found in natural environment due to the long-term human activity, and will pose adverse effects to human health. So the analysis of pesticides and antibiotics determination has important significance in food safety and environmental protection.The molecularly imprinted polymers were synthesized by bulk polymerization, using dimethoate as the template molecule. The binding capacity of the MIPs for dimethoate was investigated by equilibrium adsorption experiments. The results showed that MIPs exerted the best binding capacity for dimethoate when the proportion of dimethoate:acrylic Amide (AAM) was1:4. In molecularly imprinted solid phase extraction experiment, the sample solvent and elution solvent were optimized. The results showed that the elution effect could be the best when THF (5%acetic acid) was selected as eluent, the elution rate was98%. At the meantime, with calcein-Pd2+as a fluorescence probe, fluorescence spectrophotometry was employed to detect the concentration of dimethoate. There was a good linear relationship between the concentration of dimethoate (in the range of0.05～0.25mg/L) and the fluorescence intensity (R2=0.9981). The recovery was tested by standard addition method, using tea samples as medium. The values of recovery obtained were ranged from92%to105%.In part two, we chose cephalexin(CFX) as template molecule, acrylonitrile (AN) and acrylamide(AAM) copolymer as membrane materials, prepared molecularly imprinted membrane using sol-gel method. The conditions of the process, such as monomer ratio and the dosage of template molecule were optimized in the study. The results showed that MIMs exerted the best binding capacity for cephalexin when the proportion of CFX:AAM:AN was1:4:36. By scanning electron microscopy (sem) and Fourier infrared spectrum, structutre of the molecularly imprinted membrane was analysed. With methacryloxy fluorescein as fluorescent marker, the fluorescence quenching method used for the determination of cephalexin was established. Cephalexin and the fluorescence intensity performed a good linear relationship (R2=0.9975) when cephalexin’s concentration ranged within0.1～1.9mg/L.The recovery was tested by using urine samples as medium. The values of recovery were ranged from98%to103%.