Electrochemical sensor based on a bilayer of PPY–MWCNTs–BiCoPc composite and molecularly imprinted PoAP for sensitive recognition and determination of metolcarb

Abstract

A molecularly imprinted electrochemical sensor for metolcarb (MTMC) detection was designed and constructed by electropolymerizing a poly-o-aminophenol (PoAP) membrane in the presence of MTMC after the modification of a composite that consisted of polypyrrole (PPY), functionalized multiwalled carbon nanotubes (MWNTs) and binuclear phthalocyanine cobalt(II) sulfonate (BiCoPc) on a glassy carbon electrode (GCE) surface. The modified electrodes were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The molecularly imprinted based sensor had a good binding ability toward MTMC upon measuring the variation of the amperometric response of the oxidation–reduction probe, K₃Fe(CN)₆. The relative peak current response was found to be proportional to the concentration of MTMC in the range of 1.0 × 10⁻⁸ to 0.6 × 10⁻⁶ mol L⁻¹ with a detection limit of 7.88 × 10⁻⁹ mol L⁻¹ (S/N = 3). This desirable sensitivity may be attributed to the presence of the PPY–MWNTs–BiCoPc composite layer, which enhanced the electrode surface area and amplified the current signal. The sensor showed good selective affinity toward MTMC, compared with similar molecules, with good reproducibility and long-term stability. The prepared sensor was successfully applied to the determination of the MTMC residue in spiked vegetable samples with satisfactory recoveries ranging from 88.8% to 93.3%.