A new voltammetric sensor for electrocatalytic determination of vitamin C in fruit juices and fresh vegetable juice using modified multi-wall carbon nanotubes paste electrode

The electrocatalytic oxidation of ascorbic acid (AA) has been studied by p-aminophenol modified carbon nanotubes paste electrode (APMCNTPE). Cyclic voltammetry (CV) and chronoamperometry were used to investigate the suitability of AP as a mediator for the electrocatalytic oxidation of AA in aqueous solution. The oxidation of AA occurs at a potential about 320 mV less positive than with the unmodified carbon paste electrode at pH 7.0. The catalytic reaction rate constant, k(h) was calculated (2.257 x 10(3) M(-1)s(-1)) using chronoamperometry. The differential pulsevoltammetric (DPV) peak currents of the electrode increased linearly with the corresponding AA concentration in the range of 2.0 x 10(-7) M - 1.2 x 10(-4) M with a detection limit of 8.0 x 10(-8) M. The influence of pH and potential interfering substances on the determination of AA were studied. Finally, the proposed method was also examined as a selective, simple and precise electrochemical sensor for the determination of AA in real samples such as fruit juices and fresh vegetable juice.