a b s t r a c t A highly selective dopamine sensor was fabricated by doping polypyrrole with a sulfonated -cyclodextrin. This composite material enabled the selective sensing of dopamine in the presence of a large excess of ascorbic acid and prevented the regeneration of dopamine through the homogeneous catalytic reaction of the ascorbate anion with the dopamine-o-quinone. A single redox wave, corresponding to the oxidation of dopamine, was observed in dopamine/ascorbate mixtures, giving a truly selective dopamine sensor. The limit of detection was measured as 3.2 × 10 −6 M for dopamine.
Pyrrole was electropolymerised in a 0.01 M sulfonated βÀcyclodextrin solution to generate an adherent polypyrrole film doped with the anionic sulfonated βÀcyclodextrin, PPyÀSβCD. 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 PPyÀSβCD film was significantly better, with a linear calibration curve extending to 50 μM, with a sensitivity of 0.90 μA μM À1 cm À2 and a detection limit of 1.0  10 À6 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 5Àhydroxytryptamine and 5Àhydroxyindole acetic acid. However, interference was seen with the structurallyÀrelated epinephrine (Ep) and 3,4Àdihydroxyphenylacetic 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 MichaelisÀMenten and LineweaverÀBurk kinetics.
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