Abstract: The heterogeneous electron transfer kinetic parameters of Indigo Carmine at tin dioxide optically transparent electrode are reported here in this study. Both spectroelectrochemical and electrochemical techniques were used. In the former case, kinetic parameters were calculated from the normalized absorbance which was measured by absorbance versus time transient curve after serveral overpotential steps. A compu-ter data treatment method instead of the working curve method usually reported in literature was used in the calculation. In the later case, kinetic parameters were determined by measuring the difference of peak potentials ΔE_p of cathodic and anodic reference curve. The results obtained with both techniques had good coincidence. Further investigation shows that the value of kinetic parameters are dependent on Indigo Carmine concentration and solution pH values. It is considered as an important information for the electrochemical reduction mechanism of Indigo Carmine.

Key words: Indigo Carmine, Heterogeneous electron transfer kinetics, Spectroelectrochemistry