The present invention relates to a method for proportioning nitrate and/or nitrite ions in a solution using a copper electrode, said method being characterized in that it is carried out in constant potential mode and moreover in that it includes the steps of: i. applying a first potential to the copper electrode so as to reduce the copper oxides present on the surface of the metal copper electrode; ii. applying a second potential to the copper electrode so as to oxidize the metal copper formed in Step i into cupric ions; iii. applying a third potential to the copper electrode so as to reduce the copper oxides possibly formed in Step ii, Steps i through iii being carried out in a support electrolyte; and iv. proportioning the nitrate and/or nitrite ions of a solution to be analyzed by means of immersing the copper electrode, obtained in Step iii, in said solution to be analyzed while applying a fourth potential to the copper electrode so as to reduce the nitrate and/or nitrite ions, the support electrolyte of Steps i through iii, and the solution to be analyzed in Step iv, having a substantially neutral pH.