The selective electrochemical sensing of dopamine at a polypyrrole film doped with an anionic β−cyclodextrin

Abstract

Pyrrole was electropolymerised in a 0.01 M sulfonated β−cyclodextrin solution to generate an adherent polypyrrole film doped with the anionic sulfonated β−cyclodextrin, PPy−SβCD. This polymeric material was used as an electrochemical sensor for the detection of dopamine (DA), and compared with the sensing abilities of polypyrrole doped with several more common anionic dopants. The sensing performance of the PPy−SβCD film was significantly better, with a linear calibration curve extending to 50 μM, with a sensitivity of 0.90 μA μM−1 cm−2 and a detection limit of 1.0 × 10−6 M. Excellent selectivity was achieved and no interference was observed from a range of interference compounds, including ascorbic acid, uric acid, aspartic acid, acetylcholine, aminobutyric acid, glutamic acid, glycine, histamine, acetaminophenol 5−hydroxytryptamine and 5−hydroxyindole acetic acid. However, interference was seen with the structurally−related epinephrine (Ep) and 3,4−dihydroxyphenylacetic acid (DOPAC), with the oxidation of DA, Ep and DOPAC occurring at similar potentials. The good selectivity in the presence of the other interference species was attributed to an interaction between the cyclodextrin dopant and the protonated DA molecule which was evident when data were fitted to Michaelis−Menten and Lineweaver−Burk kinetics.