Highly selective determination of dopamine in the presence of ascorbic acid and serotonin at glassy carbon electrodes modified with carbon nanotubes dispersed in polyethylenimine

MARCELA C. RODRÍGUEZ, MARÍA D. RUBIANES, GUSTAVO A. RIVAS*; M. D. RUBIANES; G. A. RIVAS

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY

AMER SCIENTIFIC PUBLISHERS

Año: 2008 vol. 8 p. 6003 - 6009

1533-4880

We report the highly selective and sensitive voltammetric dopamine quantification in the presence of ascorbic acid and serotonin by using glassy carbon electrodes modified with a dispersion of multi-wall carbon nanotubes (MWCNT) in polyethylenimine, PEI (GCE/MWCNT-PEI) The electrocatalytic activity of the MWCNT deposited on the glassy carbon electrode has allowed an important decrease in the overvoltages for the oxidation of ascorbic acid and dopamine, making possible a clear definition of dopamine, serotonin and ascorbic acid oxidation processes. The sensitivities for dopamine in the presence and absence of 1.0 mM ascorbic acid and serotonin were (2.18 ± 0.03) x 105 µAM-1 (r = 0.9998); and (2.10 ± 0.07) x 105 µAM-1 (r = 0.9985), respectively, demonstrating the excellent performance of the GCE/MWCNT-PEI. The detection limit for dopamine in the mixture was 9.2 x 10-7 M. The R.S.D. for the determination of 50 µM dopamine using four different electrodes was 3.9 % when modified with the same MWCNT/PEI dispersion, and 4.6 % when using four different dispersions. The modified electrode has been successfully applied for recovery assays of dopamine in human blood serum. Therefore, the new sensor represents an interesting and promising alternative for the electrochemical quantification of neurotransmitters and other analytes of clinical interest.