Synthesis of surface molecularly imprinted polymer and the selective solid phase extraction of imidazole from its structural analogs

A surface molecularly imprinted polymer (MIP) was synthesized by using imidazole as the template and modified silica particles as the support material. The static adsorption, solid phase extraction (SPE) and high-performance liquid chromatography (HPLC) experiments were performed to investigate the adsorption properties and selective recognition characteristics of the polymer for imidazole and its structural analogs. It was shown that the maximum binding capacities of imidazole on the MIP and the non-imprinted polymer (NIP) were 312 and 169 μmol g⁻¹, respectively. The adsorption was fast and the adsorption equilibrium was achieved in 30 min. The binding process could be described by pseudo-second order kinetics. Compared with the corresponding non-imprinted polymer, the molecularly imprinted polymer exhibited much higher adsorption performance and selectivity for imidazole. The selective separation of imidazole from a mixture of 1-hexyl-3-methylimidazolium bromide ([C₆mim][Br]) and 2,4-dichlorophenol could be achieved on the MIP-SPE column. The recoveries of imidazole and [C₆mim][Br] were 97.6-102.7% and 12.2-17.3%, respectively, but 2,4-dichlorophenol could not be retained on the column. The surface molecularly imprinted polymer presented here may find useful application as a solid phase absorbent to separate trace imidazole in environmental water samples. This may also form the basis for our research program on the preparation and application of alkyl-imidazolium imprinted polymers.