Abstract: The symmetrical incisions occurring on oscillopolarograms obtained at two polarized micro Pt-electrodes when EDTAis present in solutions are not due to redox reaction of EDTAat Pt-electrodes. They mainly come from the adsorption of EDTAat Pt-electrodes which hinders the formation of an oxygen layer at Pt-electrodes. EDTAchanges the E_i~t curve of each Pt-electrode by shifting the upper left part of the curve to right and lower left part to left. The E~t curve obtained at two polarized micro Pt-electrodes is the superposition of E_a~t and-E_b~t EDTAshift gives sharp time lags on the final E~t curve and sharp incisions on dE/dt~E curve.

Key words: Oscillopolarographic titration, Oscillopolarograms on two polarized electrodes, Pt electrodes