Preparation of a stoichiometric molecularly imprinted polymer for auramine O and application in solid-phase extraction.

We describe a stoichiometric approach to the synthesis of molecularly imprinted polymers specific for auramine O. Using the stoichiometric interaction in molecular imprinting, no excess of binding sites is necessary and binding sites are only located inside the imprinted cavities. The free base of the template was obtained to facilitate the interaction with the monomers. Itaconic acid was selected as the functional monomer, and stoichiometric ratio of the interaction with the free base was investigated. The molecularly imprinted polymer preparation conditions such as cross-linker, molar ratio, porogen were optimized as divinylbenzene, 1:2:20 and chloroform/N,N-dimethylformamide, respectively. Under the optimum conditions, a good imprinting effect and very high selectivity were achieved. A solid-phase extraction method was developed using the molecularly imprinted polymers as a sorbent and extraction procedure was optimized. The solid-phase extraction method showed a high extraction recovery for auramine O in its hydrochloride form and free form compared to its analogues. The results strongly indicated that stoichiometric imprinting is an efficient method for development of high selectivity molecularly imprinted polymers for auramine O.

On-line determination of 4-nitrophenol by combining molecularly imprinted solid-phase extraction and fiber-optic spectrophotometry.

In the present paper, we describe a new on-line SPE system where molecular imprinting, fiber-optic detection and flow injection analysis were combined for the first time. This new system has been applied for the on line detection of 4-nitrophenol (4-NP). Initially, molecularly imprinted polymers (MIP) have been prepared for the selective extraction of 4-NP using 4-vinylpyridine and ethylene glycol dimethacrylate as functional and cross-linking monomers, respectively. Selective extraction was achieved using the designed MIP with 97% of recovery on imprinted polymer and 10% on control polymer. The system provided a high degree of accuracy, with RSDs varying between 0.7 and 1.39%. In respect of accuracy, reproducibility, and rapidity, this system is comparable with HPLC. In short, the system allows simple, fast, and accurate analyte determination with the possibility of future automation.