Determination of Dopamine in presence of Ascorbic acid by using Ultrathin Carbon Nanoparticle Composite Film Electrode

A ultrathin film (8- 19 nm) composed of carbon nanoparticles and poly(diallyldimethylammonium chloride) or CNP-PDDAC is formed in a layer-by-layer deposition process at tin-doped indium oxide (ITO) substrates. Excess positive binding sites within this film in aqueous phosphate buffer at pH 7 are quantified by adsorption of indigo carmine. Characterization of film was performed by using spectrophotometry, atomic force microscopy, impedance spectroscopy, adsorption and solution redox systems. For the mixed redox system ascorbate – dopamine in 0.1 Mphosphate buffer pH 7 cyclic voltammograms suggest a rapid and selective temporary poisoning process which causes the ascorbate oxidation to be suppressed in the second potential cycle. This effect is exploited for the detection of micromolar concentrations of dopamine in the presence of millimolar ascorbate.