A gold electrode modified with self-assembled diethylenetriaminepentaacetic acid via charge-based discrimination.

A gold electrode modified with diethylenetriaminepentaacetic acid (DTPA) has been fabricated to selectively detect dopamine (DA). The influences of experimental parameters were investigated and optimized. The anodic peak current is proportional to the concentration of DA in the range of 1.0 x 10(-7)-6.0 x 10(-3) mol L(-1) with a detection limit of 3.0 x 10(-8) mol L(-1) (S/N = 3). DA contents in the serum samples were determined; coexisting ascorbic acid (AA), uric acid (UA) and other oxidizable compounds did not cause interference to the determination. The response of AA and UA during the determination of DA could be suppressed due to the distinct charge discrimination between DA cations and the negative DTPA self-assembled layer in pH 7.4 phosphate-buffered solutions (PBS). The selectivity has been improved significantly; the response time, reproducibility and lifetime of the modified electrode are discussed.