Preparation Of Molecular Imprinting Polymer On Silica Gel Particles For Pirimicarb And Specific Binding Property

With the development of agriculture production,a lot of agrochemical have been used in farms and gardens,resulted in the serious water pollution and threatening to people.Now,there are complex agrochemical residue component in water,which might influence the analysis of sample.Therefore,it is essential to design one sort of adsorption material to selectively adsorb the analyzed molecular for solid phase extraction of the agrochemical residue,and effective monitoring the agrochemical content in water.In such subject,one sort of e molecular surfac imprinting polymer is designed,which has the strong recognition capability and selective adsorption ability for pirimicarb.Micro-sized silica gel is chemically modified by using the coupling agent 3-methacryloxypropyl trimethoxysilane(MPS).Then polymethyl acrylicacid(PMAA) is grafted on the surface of particles MPS-SiO₂ with the method of "graft from",and the grafted particle PMMA/SiO₂ is prepared.The grafted particle PMMA/SiO₂ is characterized by infrared(FTIR),thermogravimetry(TG)and scanning electronic meter(SEM).The experimental results show that the graft polymerization of methyl acrylic acid(MAA)onto the surface of silica gel particles can successfully be realized using the method of "graft from".The optimal preparation condition for silica gel with high graft degree is:temperature is 70℃,the concentration of monomer is 3% and concentration of initiator is 0.6%.As the basis of preparation of molecular surface imprinting polymer,the adsorption mechanism of PMAA/SiO₂ for pirimicarb in water is further studied.The influence of resolution style,temperature,pH and salinity on adsorption capacity is studied via ultraviolet spectral adsorption method,Zeta potential method and static adsorption method.The experimental results show that the grafted particle PMAA/SiO₂ has strong adsorption ability for pirimicarb.The driving force of the adsorption is the synergism of electrostatic,hydrogen bond and hydrophobic interaction.Among them,the electrostatic interaction is the main driving force.The adsorption capacity decreases with the enhancement of temperature or the increase of amount of salinaty;When pH＜8,the adsorption capacity increases with the increase of pH value,decreases with the increase of pH value as pH＞8,and when pH=8,the adsorption capacity has a maximum.Finally,the molecular imprinted polymethylacrylic acid on the surface of silica gel is prepared with pirimicarb as a template molecule and ethylene glycol diglycidyl ether(EGDE)as crosslinking agent,and molecular imprinting polymethylacrylic acid on silica gel,MIP-PMAA/SiO₂,is obtained.Both the selective binding properties of MIP-PMAA/SiO₂ for pirimicarb and repeated using capacity are studied,and the influence of main reaction conditions,such as pH,the component of mixed solvent and amount of crosslinking agent,on the selective adsorption ability of MIP-PMAA/SiO₂ is also examined.The experiment results show that MIP-PMAA/SiO₂ possess strong recognition capability for pirimicarb:The binding amount of propoxur,reference molecule,on MIP-PMAA/SiO₂ is much lower than that on PMAA/SiO₂,however the binding amount of pirimicarb on MIP-PMAA/SiO₂ is approximately similar to that on PMAA/SiO₂.In relation to propoxur,the selectivity coefficient of PMAA/SiO₂ for pirimicarb is 1.52,and that of MIP-PMAA/SiO₂ for pirimicarb is 12.19;and in relation to atrazine,the selectivity coefficient of MIP-PMAA/SiO₂ for pirimicarb is increased form 0.612 to 14.15. Besides,the molecular imprinted material MIP-PMAA/SiO₂ has excellent elution and regeneration property,and the adsorption capacity of MIP-PMAA/SiO₂ is still stable after using of 8 times.At the end,the results shows that main reaction conditions, such as pH,the component of mixed solvent and amount of crosslinking agent have influence on the selective adsorption capability of MIP-PMAA/SiO₂,and the optimal preparation conditions of MIP-PMAA/SiO₂ is determined:pH value is 8,the content of ethanol is 50%and the ratio of amount of crossing agent and amount of grafted MAA is 1:3.