On the amperometric detection and electrocatalytic analysis of ascorbic acid and dopamine using a poly(acriflavine)-modified electrode

In this study, poly(acriflavine), PAF, a compact thin film, was electropolymerized on the glassy carbon (GC) electrode by cyclic voltammetry for sensing ascorbic acid (AA) and dopamine (DA). When comparing with the literatures, it was found that our GC/PAF electrode offers the second largest peak separation, 255 mV, between AA and DA at pH 7 owing to the positive nature of the PAF film. The diffusion coefficient and the intrinsic rate constant of AA were determined to be 1.84 × 10−6 cm2 s−1 and 0.0032 cm s−1, respectively, by the rotating disc electrode (RDE) analysis. The effect of carbon nanotube (CNT) loading was also discussed in the study. For an amperometric detection of AA in a flow injection system at 0.2 V (vs. Ag/AgCl/sat′d KCl), the sensitivity, linear range, response time, recovery time and limit of detection are 116 μA mM−1 cm−2, 3–200 μM, <2 s, 5–10 s and 1.5 μM, respectively. In the aspect of selectivity, the common interferences, DA and uric acid (UA), contribute 6.6% and 0.7% extra current, respectively for equal molar AA. For the commercial vitamin C tablet, the monitoring error caused by the GC/PAF electrode prepared in this study is only 2.6% as compared to the standard value obtained from a high-performance liquid chromatography-electrochemical (HPLC-EC) detection.