Carbon nanotubes paste electrodes modified with a melanic polymer: Analytical applications for the sensitive and selective quantification of dopamine

This work describes the advantages of carbon nanotubes paste electrodes (CNTPE) modified with a melanic polymer for the highly sensitive and selective quantification of dopamine. The polymer is electrogenerated from a 3.0 × 10−3 M l-dopa solution (in a 0.050 M phosphate buffer pH 7.40) by applying 0.80 V for 120 min. Two strategies for dopamine quantification are described, the amperometric detection at 0.200 V using 1.0 × 10−3 M ascorbic acid in the measurement solution to improve the sensitivity of the assay; and the adsorptive stripping detection with medium exchange using differential pulse voltammetry (DPV) as transduction mode. Detection limits of 2.0 nM and 20 nM were obtained with amperometry and adsorptive stripping, respectively. The interference of 5.0 × 10−4 M ascorbic acid and 5.0 × 10−5 M dopac was really negligible in both cases, demonstrating the advantages of the melanic polymer as permselective layer.