Abstract: The mechanisms of electrochemical reduction and electrochemical oxidation of Indigo Carmine were investigated by means of thin-layer spectroelectrochemical tech-nique at a SnO_2-quartz optically transparent electrode cell.
The formal potentials and electron transfer numbers of the reduction of Indigo Carmine were determined at different pHs. The results showed that the reduction of Indigo Carmine at SnO_2 electrode is a quasireversible two-electron transfer process and its oxidation is a irreversible electron transfer process. The mechanisms of the electroreduction and electro-oxidation were discussed on the basis of the spectrum recorded in situ during the electrochemical process.