辛硫磷分子印迹聚合物修饰电极的制备及应用研究

Preparation and Application of Electrode Modifided with Phoxim Molecular Imprinted Polymer

以辛硫磷为模板分子,甲基丙烯酸（MAA）为功能单体,乙二醇二甲基丙烯酸酯（EDMA）为交联剂,偶氮二异丁腈（AIBN）为引发剂,在乙腈中沉淀聚合,研究制备了辛硫磷分子印迹聚合物（MIPs）,并采用红外光谱、扫描电镜对合成的聚合物进行表征.Scatchard分析表明MIPs对辛硫磷有两种结合方式,最大表观吸附量（Qmax）和平衡解离常数（KD）分别为：Qmax1=70.58 μmol/g,R1=0.72 mmol/L;Qmax2=531.8 μmol/g,KD2=7.80 mmol/L.将聚氯乙烯（PVC）5 mg和15 mg印迹聚合物超声分散于20mL四氢呋喃（THF）中,取32 μL分散液涂敷在玻碳电极上制备成辛硫磷分子印迹聚合物修饰电极,线性伏安法（LSV）检测.选择开路富集时间为5min,于0.03 mol/L HCl-0.02 mol/L KCl溶液（pH 2.2）中,辛硫磷在1.2×10-7～6.0×10-3 mol/L浓度范围内,其在修饰电极上的还原峰电流与浓度的负对数呈良好的线性关系,检出限为6.0 ×10-8mol/L.用分子印迹聚合物修饰电极对实际样品进行分析,回收率为93.8％～ 96.2％.将印迹聚合物修饰电极对辛硫磷及其类似物（如三唑磷、毒死蜱、乐果等）进行检测,该电极对辛硫磷显示了良好的选择性和灵敏度.

Using phoxim as template, a-methacrylic aid（MAA） as monomer, ethylene glycol dime- thacrylate（EDMA） as cross-linker and 2, 2-azobisisobutyronitrile （AIBN） as initiator, the phoxim molecular imprinted polymers （MIPs） was synthesized by polymerization in acetonitrile. MIPs were characterized by infrared spectroscopy and scanning electron microscopy. Scatchard plot analysis re- vealed that two kinds of different binding sites existed in MIPs, in which the maximum amounts of ap- parent binding and dissociation constants of binding sites were as follows： Qmax1 = 70. 58 μmol/g, KD1 = 0. 72 mmol/L; Qmax2 = 531.8 μmol/g, KD2 = 7. 80 mmol/L. 5 mg polyvinyl chloride （ PVC ） and 15 mg imprinted polymer were ultrasonically dispersed in 20 mL of tetrahydrofuran （THF）, phoxim molecularly imprinted polymer modified electrode was prepared by adding 32 μL the disper- sion dropwise onto the surface of glassy carbon electrode （GCE）. Linear sweep voltammetry （LSV） was employed in the process of electrochemical measurements. The experimental results showed that the optimum acidity of 0. 03 mol/L HC1 - 0. 02 mol/L KC1 solution is pH 2. 2, and the optimum incu- bation time is 5 min. A highly linear response to phoxim in the concentration of 1.2 ×10-7 - 6. 0 × 10-3 mol · L-1 was observed, with a detection limit of 6. 0 × 10-8 moL/L estimated at a signal -noise ratio of 3. The sensor was applied in the analysis of phoxim in real sample with recoveries of 93.8% - 96. 20./0. The electrode modified with phoxim molecular imprinted polymer exhibited a good selectivity and sensitivity to phoxim when it was exposed to a series of closely related compounds with similar elec-trochemical characteristics, e. g. triazophos, chlorpyrifos and dimethoate.