Methods and systems for simultaneously measuring concentration of two or more different cations in solution. The methods include the steps of applying a steady state polarization technique to a solution comprising two or more different cations; measuring the limiting currents of the solution; and correlating the limiting currents with the concentration of the different cations. The system includes a working electrode; a potentiostat; a counter electrode; a reference electrode; a solution comprising different cations to be analyzed; and a model for correlating the limiting currents with the concentration of the pair cations. The working electrode may be any electrode compatible with the media, including noble metals, carbon, or combinations thereof. In some embodiments, the working electrode is a rotating disk electrode (RDE).