Voltammetric determination of ascorbic acid and dopamine in the same sample at the surface of a carbon paste electrode modified with polypyrrole/ferrocyanide films

Functionalized polypyrrole film were prepared by incorporation of [Fe(CN)6]4− as a doping anion, during the electropolymerization of pyrrole onto a carbon paste electrode in an aqueous solution by potentiostatic method. The electrochemical behavior of dopamine (DA) and ascorbic acid (AA) in one solution was studied at the surface of bare and modified carbon paste electrodes using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differntial pulse voltammetry (DPV) methods. The well separated anodic peaks for oxidation of DA and AA were observed at the surface of the modified carbon paste electrode under optimum condition (pH 6.00), which can be used for determination of these species simultaneously in mixture by LSV and DPV methods. The linear analytical curves were obtained in the ranges of 0.10–1.00 mM and 0.10–0.95 mM for ascorbic acid and 0.10–1.20 mM and 0.20–0.95 mM for dopamine concentrations using LSV and DPV methods, respectively. The detection limits (2σ) were determined as 3.38 × 10−5 M and 1.34 × 10−5 M of ascorbic acid and 3.86 × 10−5 M and 1.51 × 10−5 M of dopamine by CV and DPV methods.