Chromatographic Separation of Xanthine Derivatives on Single and Mixed-Template Imprinted Polymers

Center for Advanced Bioseparation Technology and Dept. of Chem. Eng., Inha University, Incheon 402-751, KoreaReceived November 29, 2003We developed in the present study molecular imprinted polymers (MIPs), using single templates (pentoxifylline,caffeine and theophylline) and mixed-templates (pentoxifylline-caffeine, pentoxifylline-theophylline andcaffeine-theophylline). The MIPs were prepared with methacrylic acid (MAA) as the monomer, ethyleneglycol dimetharylate (EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. Theobtained polymer particles (particle size after grinding was about 25-35 µm) were packed into a HPLC column(3.9 mm i.d. × 150 mm). The selectivity and chromatographic characteristics of the MIPs were studied usingacetonitrile as the mobile phase at a flow rate of 0.8 mL/min. UV detector wavelength was set at 270 nm.Different single template MIPs showed different molecular recognitions to the templates and the structurallyanalogues, according to the rigidity and steric hindrance of the compounds. Recognition was improved on themixed-template MIPs as a result of the cooperation or sum effect of the templates, whereas on thepentoxifylline-theophylline imprinted polymer, the highest selectivity and affinity were obtained. Separationsof the test compounds on different polymers were also investigated.Key Words : Molecular imprinted polymers (MIPs) , Xanthine derivatives, SeparationIntroductionThe technique of molecular imprinting consists of the self-assembly of a functional monomer and a template moleculein solution followed by the co-polymerization of the func-tional monomer and an excess of an appropriate crosslinkingmonomer. After removing the small molecule, the resultingnetwork polymer exhibits a significantly higher affinity forthe molecule used as the template than for similar molecules,including closely related isomers.