Preparation of molecularly imprinted polymer for sinomenine and study on its molecular recognition mechanism

A sinomenine (SIN) molecule-imprinted monolithic stationary phase (MIMSP) with specific recognition for SIN was prepared by in situ technique, utilizing methacrylic acid (MAA) as a function monomer, ethylene glycol dimethacrylate (EDMA) as a cross-linking agent, and low-polar solvents (toluene and dodecanol) as porogenic solvents. The selectivity of the polymers for SIN was evaluated by high performance liquid chromatography (HPLC). Some chromatographic conditions, such as the column temperature, the flow rate and the composition of the mobile phase, were changed in order to characterize the chromatographic procedure. SIN could be separated from some other structural analogues, including morphine, codeine, codethyline and magnoflorine, under optimized conditions. Scatchard analysis showed that two classes of binding sites existed in the SIN-imprinted polymers, with their dissociation constants estimated to be 7.257×10−5 and 3.828×10−3 mol l−1, respectively. Compared with the SIN-imprinted polymers, the non-imprinted polymers prepared using the same method but in the absence of SIN did not exhibit the specific molecular selectivity, which suggests that the specific molecule-recognition ability of the SIN-imprinted polymers was largely ascribed to the imprinting effect.