Employing nylon membrane as the supported membrane, caffeine as template, acrylamide (AA) as functional monomer and ethyleneglycol dimethyacrylate (EGDMA) as cross linker, molecularly imprinted composite membrane was prepared by using a surface thermal-polymerization method. The characterization of the caffeine molecularly imprinted membrane was performed with infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and liquid chromatography techniques in detail. The results show that the imprinted membrane exhibits excellent selectivity for the template with the selectivity factor 2.30 and can be better applied to separate and enrich tea extract with an enrichment factor 10.52. The imprinted membrane exhibited better combination capabilities to the template molecule with two imprinted binding sites. The maximum apparent amounts for higher binding site and lower binding site are 0.146 and 0.330 μmol/g, respectively.

Key words: caffeine, imprinted membrane, preparation, evaluation