Molecularly imprinted electrochemical sensor, formed on Ag screen-printed electrodes, for the enantioselective recognition of d and l phenylalanine

Abstract

In this study, electrochemical sensors for the enantioselective recognition of d and l phenylalanine were prepared using a molecular imprinting technique in which the electro-polymerization of pyrrole was carried out by Chronopotentiometry(CP) with the target molecules being present on a Ag screen printed electrode's (SPE) surface. The sensing performance was evaluated by multi-potential steps at 0 and 2V(vs. Ag/AgCl) held for 1s and 2s, respectively, for 20 cycles (with the two enantiomers being present at the same concentration). The individual selectivity's for l and d- phenylalanine on their respective imprinted films were estimated to be L/D = 23.480 ± 2.844/1 and D/L = 19.134 ± 1.870/1 respectively, based on the current change between 0 and 2V (vs. Ag/AgCl) with the two enantiomers being present at the same concentration (10mM). Several parameters affecting recognition ability were investigated including: cross-selectivity of d and l- phenylalanine imprinted film, phenylalanine concentration effects, interfering species, deactivation and the storage life of electrode. The phenylalanine imprinted films were also characterized by AC impedance, chronoamperometry, Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscope(SEM), and Energy Dispersive X-Ray Spectroscopy (EDS). Finally, a recognition mechanism for the interaction of the polypyrrole film with its template under the influence of applied negative and positive potentials is proposed.