PREPARATION OF URSOLIC ACID IMPRINTED POLYMERS BASED ON MULTI-WALLED CARBON NANOTUBES AND THEIR APPLICATION IN SOLID PHASE EXTRACTION

Abstract

A novel surface molecularly imprinted polymer was synthesized using poly(vinyl alcohol) modified multi-walled carbon nanotubes(MWCNTs) as supporting matrix,ursolic acid(UA) as the template molecule,methacrylic acid(MAA) as the functional monomer and ethylene glycol dimethacrylate(EGDMA) as the cross-linking agent.Effect of different molar ratios of the functional monomer to the template on the performance of the synthesized MWCNTs-MIPs was discussed and the results showed that the optimum ratio was 4∶1.The multi-walled carbon nanotubes-molecularly imprinted polymers(MWCNTs-MIPs) were characterized by Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM).The results showed that a stable imprinted layer was grafted on the MWCNTs surface successfully.The adsorption properties were demonstrated by static adsorption and adsorption kinetic experiments.The results demonstrated that the MWCNTs-MIPs had specific selectivity for UA,yielding a maximum adsorption capacity of 53.1 μmol/g and the equilibrium time took about 60 min.Solid phase extraction condition was optimized,and the optimal condition was washing with 100% methanol and eluting with 10% acetic acid methanol solution.The solid-phase extraction column packed with MWCNTs-MIPs could be applied to separate ursolic acid(UA) from similar structure oleanolic acid(OA).