Size-selective recognition of catecholamines by molecular imprinting on silica-alumina gel.

The preparation of a catecholamine receptor was carried out using a molecular imprinting method with silica-alumina gel to form complementary structures for template recognition. The molecularly imprinted polymer (MIP) was synthesized by the condensation of silicate from tetraethyl orthosilictate (TEOS) under hydrothermal conditions at 60 degrees C. Aluminum chloride was added as a functional monomer to increase the material's rebinding ability. The selectivity of the MIP receptor prepared with different ratios of template to Si and Al, was examined with seven analytes including: dopamine, epinephrine, norepinephrine, ascorbic acid, homovanillic acid, uric acid, and l-tyrosine. The results showed a size selective effect for the receptors with respect to the recognition of the catecholamines. Some factors affecting the recognition ability were investigated including: the solution pH of analytes, surface capping on the MIP, and the imprinting pH of the silica-alumina solution. Also, the catecholamine MIP films on quartz crystal microbalance (QCM) electrodes were fabricated as sensors for in situ monitoring of the analytes in a 2-propanol solution.