Preparation And Performance Study Of Nicotinic Acid-Imprinted Polymers With Silica Gel As Sacrificial Carrier

Molecularly imprinting technology(MIT) is a new isolation technology, which can be uesd as a fast, simple and effective pre-preparation method in order to promote performance of model analysis instrument.In this research, silica gel was taken as sacrificial carrier, while molecularly imprinted polymers (MIPs) were prepared, using acrylamide as the functional monomer and ethylene glycol dimethacrylate as the cross-linker in the presence of template molecule of nicotinic acid. The influences of different kinds of monomer, as well the dosages of monomer, cross-linker and silica gel with different time and temperature of polymerization toward the adsorptive properties of MIPs were investigated one by one. The optimum process condition was confirmed by orthogonal experiment. Then MIPs were measured by scan electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis. The selectivity and binding ability of MIPs were evaluated by static adsorption test, plate chromatography test and Scatchard analysis. Then we prepared the MIPs-SPE column. The optimum condition of mobile phase was investigated. In the last part, by combining the techniques of supercritical CO₂ extraction and ultrasonic, MIPs were applied to abstract nicotinic acid from laver samples.The research had confirmed the optimum process condition with silica gel as sacrificial carrier as follow: the dosages of template was 1.5mmol,the template/monomer(AM) ratio was 2:3,the dosages of cross-linker was 50mmol,the dosages of silica gel was 40g, and the polymerization time and temperature were 16h and 60℃. The binding capacity of MIPs prepared at this optimum condition reached 78.5μmol/g. MIPs were compared with NMIPs while niacinamide was chosen as a competitive material, the separation factor was estimated to be 2.76, and the separation factor ratio reached 2.14. By using Scatchard analytical method, the research on binding performances of the prepared polymers demonstrated good specific adsorption ability to template. The equilibrium dissociation constant reached 4.08 mmol/L, and the maximum binding site reached 97.1μmol/g. The result of Thermogravimetric Analysis showed that the thermal stability of MIPs was changed for the adsorption of nicotinic acid. The prepared MIPs showed good service durability, which was confirmed by repeatability experiments. By investigating the influence of water capacity, pH value and flow rate of mobile phase toward the recognition and adsorption capability of MIPs-SPE column, the best mobile phase condition was confirmed: the water capacity was 10%, the pH value was 5 and the flow rate was 1ml/min. In the last part of the research, the MIPs-SPE was combined to the techniques of supercritical CO₂ extraction and ultrasonic assistant extraction technology for the application in the extraction of nicotinic acid from laver samples. The application showed good result, the productive rate of nicotinic acid reached 68.6%.