Ion Selective Electrode for Dopamine Based on a MolecularlyImprinted Polymer

An all-solid-state ISE for dopamine (DAHCl) has been developed based on a screen printed graphite electrode modified with a multiwalled carbon nanotubes layer as an ion to electron transducer. The selective membrane is an acrylic polymer molecularly imprinted with the ion of interest (MIP). The polymer is made up of methacrylic acid as functional monomer and ethyleneglycole dimethacrylate as cross linker. The polymerization at 75 degrees centigrades in the presence of AIBN as initiator was carried out in situ, directly over the CNT-modified screen printed graphite. The specific site obtained after polymerization and template elution can be considered as the ionophore, and the carboxylic groups as the cation exchanger groups, similarly to the usual ISE membrane. The specificity of the electrode was evaluated by voltammetric methods, and was very good. The potential of the electrode, measured against a double junction Ag/AgCl/KCl (sat.), linearly increases with the dopamine concentration at concentration higher than 10^(-4) M, but only in salt solution at least 0.1 M. The sensibility was less than nernstian. Not any potential increase was found for the electrode modified with not imprinted polymer (NIP) at the same conditions. The effect of ions in solution was particularly considered.