Preparation and Evaluation of Uniform-Sized Sol-Gel Theophylline Imprinted Microspheres as Solid Phase Extraction Sorbent

A highly selective imprinted amino-functionalized silica gel microsphere was prepared by a simple molecular imprinting technique with a sol-gel process. Theophylline was used as template; 3-aminopropyltrimethoxysilane (APTMS) as functional monomer and tetraethylorthosilicate (TEOS) as reticulating agent. These theophylline imprinted silica microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron micrographs (SEM), thermogravimetric analysis (TGA), and high performance liquid chromatography (HPLC) in detail. The results showed that monodispersive APTMS-silica imprinted microspheres with size of 250nm were synthesized successfully. Two kind of binding sites exist between the sol-gel imprinted microspheres and theophylline with KD and Qmax for the higher affinity binding parameters was 1.89g/mL and 7.47g/mg dry polymers, and for the lower affinity binding sites were found to be 0.18g/mL and 3.47g/mg dry polymers, respectively. Packed in column, the imprinted microspheres were employed to extract theophylline from green tea successfully.