| Molecular imprinting technique has antibody’s properties Specificity, high selectivity, high strength and other advantages, compared with natural antibody. Molecular imprinting technique has the advantages of simple preparation. The template molecule recyclable reuse. Causing great concerned in the field of veterinary medicine residue analysis. In this paper, the molecular imprinting technique is applied to four kinds of nitrofuran drugs nitrofuran. The four kinds of nitrifuran durgs was acted template molecule. Methacrylic acid,2-vinyl pyridine and methyl methacrylate was acted functional monomer, ethylene glycol dimethacrylate, N, N’-methylene acrylamide and any proportion of them as the functional monomers. Nitrofurans molecularly imprinted polymers were synthesized by sacrificial silica gel method respectively which precipitated with methanol acetic acid to elution the poly template molecule complexes.First of all, THE orthogonal test was used in bulk polymerization method. Solid-phase extraction cartridge recycling rate was acted the performance index. The optimal system of polymer preparation conditions, bulk polymerization method imprinted polymer microspheres were selected initially. The best preparation conditions:functional monomer: MAA:MMA=3:1, crosslinker agent:EGDMA, template monomer crosslinker ratio for 1:6:40 and pre polymerization time:20h, polymerization time for 24h, the polymerization temperature is 65℃. The maximum static adsorption capacity was 1.49mg/g.Secondly, Silica gel as the skeleton in sacrifice silica gel method, which surrounded a nitrofuran molecularly imprinted polymer. The microspheres silica was reacting to elution under the hydrofluoric acid washing. After the methanol acetic acid eluted, dryed, the polymer microspheres of nitrofuran drugs was formed. Single factor analysis was used in this method. The monomer dosage’s, the amount of crosslinking agent, the dosage of silica gel and triggered agent influence was considered.Thirdly, Precipitation polymerization which does not need grinding and screening steps to reach the corresponding size of the microspheres is different from the bulk polymerization method. The molecularly imprinted polymer was sheared by the solvent and shaked severely to control the size of the synthesis of molecularly imprinted polymers. Compared with sacrificial silica gel method, single factor analysis was also used in this method. The optimal conditions were obtained by the studying of the proportion of solvent, solvent dosage, monomer and crosslinking agent. It was acetonitrile as solvent,41mL; template monomer cross-linking agent 1:12:80. The maximum static adsorption amount was 2mg/g in precipitation polymerization method.Comparison of the three methods’static adsorption and recovery rate, we obtained that sacrificial silica gel was the best method of synthesis of molecularly imprinted polymer. The polymer of maximum adsorption capacity was:furaltadone 1.92mg/g, furazolidone 1.44mg/g, nitrofurazone 2.33mg/g, nitrofurantoin for 1.50mg/g. The average recovery rate was: furaltadone for 98.4%, furazolidone for 86%, nitrofurazone 98.6%, nitrofurantoin for 88.4%, the relative standard deviation (RSD) was 3.3%.Finally, the polymers were characterized by the static adsorption test, infrared spectroscopy, scanning electron microscope (SEM), and the polymer microspheres were filled to a 200mg/3ml solid-phase extraction. The MIP-SPE was used in in the sample’ nitrofuran drugs test. The conditions for the use of homemade hometown extraction column were discussed. By using self-made molecularly imprinted column combination with HPLC, a new nitrofuran content analysis method in feed was established. The limit of detection was 0.05mg/kg. Four nitrofuran drugs recovery rate reached 90%～120% and the relative standard deviation was 6.0%. |
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