Recognition Of Molecularly Imprinted Polymers For Trace Of Drugs In Aqueous Solution

Molecularly imprinted polymers (MIPs) as artificial receptors are currently under investigation in numerous applications, especially in chemical sensor. MIPs are usually as molecular recognition membranes on chemical sensing systems. The sensing systems are based on the analyte bound to the MIPs membrane itself reacts on the surface of the solid support on which MIPs are prepared, or the characteristic alteration of MIPs membrane caused by binding the analyte. Since the preparation of MIPs is simple and inexpensive and applicable to various molecules, MIPs have been ideal candidates as recognition elements for sensor.In this work, a voltammetric sensor for nicotinic acid (NA) was developed by creating a membrane layer of MIPs on the surface of a glassy carbon electrode. SEM images showed that the surfaces of the NA-MIP-modified electrode and the NIP-electrode have no obvious difference. But the NA-MIP-modified electrode exhibited high affinity and selectivity for the template compound to closely related analogs. The different characters between the two electrodes were only due to the imprinted cavities. NA can diffuse through the membrane to the electrode surface more easily than other chemicals, followed by being reduced, because of the imprinting effect.In this work, an electrochemical sensor for phenylephrine based on molecular imprinting technology was also developed. As the degree of cross-linking increased, the size of the pores in the membrane was decrease. SEM images revealed the gradual change on the surface morphology of modified electrodes. The molar ratio 4:40 of functional monomer and cross-linking was the optimum. The MIP-modified electrode exhibited higher affinity and selectivity to the template molecule than closely related analogue, while the NIP- modified electrode had no this feature. The sensor could be applied to determine the phenylephrine in complex samples, such as tablet and human urine.This allows the conclusion that the molecular imprinting is effective to give selectivity to analytes in sensing. The sensor exhibited good analytical feature in terms of sensitivity, selectivity. Therefore MIPs are very promising elements for highly selective analytical sensor.However, what we hope to achieve is the development of MIPs that contain a more homogeneous binding site population, have a higher affinity for the target ananlytes, and can be use in aqueous solvents. We applied a template analogue imprinting strategy to imprint dopamine. We found that dummy template molecularly imprinted polymers prepared by precipitation polymerization in toluene/chloroform (V/V, 3/1) displayed good affinity to the target. The binding behavior of these MIPs, which can be modeled by the Langmuir-Freundlich Isother, is a typicaly continuous distribution models. Heterogeneity, total number of binding sites, and average binding affinity can be measure. This allows the rapid evaluation of binding properties MIPs, and quantitative comparisons. This part of our work makes good senses to the coming work.