VOLTAMMETRIC AND AMPEROMETRIC DETERMINATION OF ASCORBIC-ACID AT A CHEMICALLY MODIFIED CARBON-FIBER MICROELECTRODE

A carbon fibre microelectrode was modified by electrodeposition of a t hin copper-heptacyanonitrosylferrate (CuHNF) film on its surface. The film showed the ability to catalyse electrochemical oxidation of ascor bic acid. The catalytic reaction was limited either by diffusion, or b y the electrochemical reaction of the catalyst. A linear, cyclic volta mmetric response for ascorbic acid was obtained between 5.0 x 10(-5) a nd 6.0 x 10(-3)M. By amperometric measurements the linear range could be extended to 8.0 x 10(-6)-2.0 x 10(-3)M. The modified electrode show ed good stability and reproducibility.