Synthesis of a pH dependent covalent imprinted polymer able to recognize organotin species

Abstract

The covalent imprinting approach has for the first time been successfully applied for the synthesis of an imprinted polymer able to recognize organotin species. The synthesis has been accomplished by co-polymerization of the complex Bu₂SnO-m-vinylbenzoin as the imprinting template plus co-monomer sodium methacrylate, and ethylene glycol dimethacrylate as cross-linker. The imprinting effect has been evidenced within the narrow pH range 2.5 < pH < 3.5. At lower pH values, the imprinting effect is prevented by the exclusive existence of non-specific interactions, whereas pH > 3.5 provokes a strong rebind of the template in both imprinted and non-imprinted polymers. This pH dependency can be explained as a selective chemical modification which reduces bind diversity following a model based on enolization by protonation of the specific cavities. Characterization of the adsorption isotherms showed good agreement with the Langmuir–Freundlich (LF) model, presenting quite homogeneous binding sites for a bulk material and high capacity in the imprinting pH range. In addition, the affinity spectrum (AS) method has been represented showing the typical profiles of LF isotherm for both sub-saturation and saturation levels, being in general agreement with the encountered values for fitting coefficients. The covalent molecular imprinted polymer has been succesfully evaluated in a SPE process for further OTC determination in the certified mussel tissue (CRM 477)