Electrocatalytic oxidation of 3,4-dihydroxyphenylacetic acid at a glassy carbon electrode modified with single-wall carbon nanotubes

The voltammetric behavior of 3,4-dihydroxyphenylacetic acid (DOPAC was studied at a glassy carbon (GC electrode modified with single-wall carbon nanotubes (SWNTs). In 0.1 M HAc-NaAc buffer solution (pH 4.4), the SWNT-modified electrode shows high electrocatalytic activity toward oxidation of DOPAC. One well-defined redox couple is obtained. The peak current increases linearly with the concentration of DOPAC in the range of 1.0 x 10(-) (6) - 1.2 x 10(-4) M. The detection limit is 4.0 x 10(-7) M. The results indicate that DOPAC undergoes a two-electron oxidation to upsilon -quinone followed by a dimerization reaction. Rate constant for this dimerization reaction was calculated to be 2. 10 x 10(3) dm(3) mol(-1) s (-1) . The SWNT was characterized with scanning electron microscope (SEM). This SWNT-modified electrode can also separate the electrochemical responses of DOPAC and 5-hydroxytryptamine (5HT). (C) 2001 Elsevier Science Ltd. All rights reserved.