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Abstract
The successful pulsed amperometric detection of underivatized amino acids have been
carried out in an acidic media on a polypyrrole (PPy) modified Cu electrode. The formation
of PPy film doped with glutamate (glu) on a Cu electrode surface changes the mechanism
of Cu dissolution. After application of multistep potential waveform, the PPy film
was glu free due to the electro-reduction and overoxidation. High anodic potential
polarization treatment yielded partially overoxidized PPy film as long as the Cu surface
dissolution and amino acid permeation through the film was well controlled. This overoxidized
PPy film acted as a charge and size exclusion barrier in order to improve the selectivity
and stability of a Cu electrode. Various process parameters such as film modification
time, detection and cleaning potential and pH of solution have been optimized to maximize
the beneficial electrocatalytic properties of the electrode surface. At an optimized
condition, detection limits for positively charged histidine and arginine are 19 and
22 pg respectively, whereas the neutral amino acids detected in amounts of 0.9-2.3
ng. Furthermore, the PPy coated Cu electrode response was long lived, stable and reproducible.