Synthesis and characterization of a surface imprinting silica gel polymer for the resolution of tetrahydropalmatine enantiomers

An L-tetrahydropalmatine (L-THP) imprinted silica gel polymer functionalized with aminated groups was prepared with surface imprinting technique by using L-THP as template, grafted silica gel as support, methacrylic acid as functional monomer and ethylene glycol dimethyl acrylate as cross-linker by solution polymerization. The optimum ratio of template, functional monomer, and cross-linker were found to be 1:4:20 and the conditions of synthesis were 50°C for 18 h. The surface imprinting silica gel polymer of L-THP was used as a sorbent for L-THP adsorption and showed better adsorption capacity of L-THP than that of non-imprinted polymers. Then the surface imprinting silica gel polymer of L-THP was filled into the cartridges as the adsorbents of solid-phase extraction, and the mean recoveries of L-THP and D-tetrahydropalmatine were 70.1% and 17.1% with 2.8% and 3.0% of relative standard deviation, respectively.