Synthesis of Chlorogenic Acid Imprinted Chromatographic Packing by Surface-initiated Atom Transfer Radical Polymerization and Its Application

A novel chromatographic packing of chlorogenic acid（CGA） molecularly imprinted polymer（MIP） based on the 5.0 ~tm silica was prepared by surface initiated atom transfer radical polymerization（SI-ATRP） with 4-vinylpyridine（4-VP） as functional monomer, ethyl glycol dimethacrylate（EDMA） as cross-linker in the mixture of methanol and water（7：3, volume ratio） under mild reaction conditions. The characteristics of CGA MIP were investi- gated by elemental analysis, thermogravimetric analysis（TGA）, Fourier transform infrared spectrometry（FTIR） and atomic force microscopy（AFM）. The effects of some chromatographic conditions such as mobile phase composition and temperature on the retention time were investigated. The adsorption capacity of the stationary phase for com- pounds was determined by frontal chromatographic technique. The results show that Freundlich isotherm fits the ex- perimental adsorption isotherm data better than Langmuir model does. The relatively high heterogeneity index values regressed with the Freundlich isotherm suggest the formation of fairly homogeneous MIP. Thermodynamic data（AAH and AAS） obtained by van＇t Hoff plots reveal an entropy-controlled separation. The CGA MIP column was shown to be successful for the separation and purification of chlorogenic acid from the extract of Honeysuckle.