Preparation Of The Solid-phase Extraction And The Potentiometic Sensor Baesd On Molecularly Imprinted Polymer

Molecular imprinting technique is a new technology with rapid development at present. Molecularly imprinted polymer (MIP), prepared by the molecular imprinting technique, has been used successfully in many fields such as separation, immunoassay, mimetic enzyme and sensor as its molecular recognition characteristics, and has become a hotspot in research.This paper takes caffeine and DPHP as object of study, makes use of the molecular recognition characteristics of MIP to prepare the solid-phase extraction (SPE) sorbent and sensitive membrane of potentiometric sensor. The new methods of caffeine MIP-SPE-HPLC, DPHP MIP-SPE-HPLC and potentiometric analysis developed can provide technical support for the analysis of trace caffeine and DPHP in food and medicine. The main contents are as following.1. The molecular imprinted polymer (MIP) with high selectivity to di(2-propylheptyl) phthalate(DPHP) was synthesized by bulk polymerization with dioctyl phthalate(DOP) as dummy template, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker. The binding ability on template and functional monomer was investigated by UV. Compared with the functional monomer acrylic acid (AA), MAA showed stronger binding capacity to DOP and the best combination ratio of6:1. The selective adsorption performance of MIP for DPHP, DOP, dimethyl phthalate (DMP) and dibutyl phthalate (DBP) was investigated using the prepared MIP as high performance liquid chromatographic column packing. It is found than the prepared MIP showed higher retention ability and selectivity for DPHP. Using the prepared MIP as a solid-phase extraction (SPE) sorbent, the effects of the type and amount of elution solvents on the recovery of DPHP were investigated. After optimization of SPE profile, the DPHP extraction recovery of96.8%was obtained when the following procedure was applied to MIPs cartridge:conditioning with2mL methanol, loading with1mL methanol, washing with1mL methanol-water (9:1,V/V), eluting with5mL methanol-acetic acid (9:1,V/V). The recovery of DPHP on NIPs cartridge was only52.9%. The MIP-SPE-HPLC method was applied to the pharmacokinetic study by determining the concentrations of DPHP in rabbit serum. The recoveries of spiked DPHP in rabbit serum ranged from90.5%～91.2%.2. The molecular imprinted polymer (MIP) was synthesized by precipitation polymerization with caffeine as template, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linker. And its molecular recognition characteristics to caffeine were studied by infrared spectroscopy, scanning electron microscopy and static adsorption experiments. The results showed that this polymer could specially recognize caffeine. The polymer was used as a solid-phase extraction (SPE) sorbent, for selective trapping and pre-concentration of caffeine. After optimization of SPE profile, it was found that the extraction recovery of97.1%was obtained with loading in water, washing with1mL water, eluting with6mL methanol-acetic acid (9:1, V/V). In comparison with NIP column and commercially available Cis column, the MIP-SPE column exhibited higher extraction efficiency. The developed MIP-SPE-HPLC method was successfully applied to the determination of caffeine in tea and human plasma after administration of tea, with satisfactory results.3. The caffeine MIP was used as sensitive material for the preparation of coated wire electrode. Taking the electrode obtained as indicator electrode, and calomel electrode as reference electrode to investigate the influence of membrane composition and solution ph on electropotential response. Meanwhile, electivity coefficients, response time, life, stability and response curve of the electrode were investigated. The sensor showed Nernst response for caffeine was over the concentration range of1.0×10-8to1.0×10-5mol·L-1. The linear equation is y=94.95x-69.15(R=0.9998). The sensor is with the detection limit of1.0×10-9mol·L-1and can be used more than100times. The caffeine coated wire electrode has been successfully applied to test caffeine of syrup sample.