An apparatus to detect more than one analyte in a solution comprising at least one electrode in contact with the solution, at least two dyes including a first dye and a second dye, and an electrochemically active agent, where the solution has a pH, the electrode is configured to modulate the pH of the solution by oxidizing or reducing the electrochemically active agent, the first dye and the second dye fluoresce at different pH levels, fluorescence of the first dye is used to indicate the presence of a first analyte, and fluorescence of the second dye is used to indicate the presence of a second analyte. Methods of detecting multiple analytes in a solution are also provided.