Use of Butler–Volmer treatment to assess the capability of the voltammetric ion sensors: Application to a PPy/DBS film for cations detection

In this work, the Butler–Volmer formalism has been used to obtain a new equation to assess the calibration of voltammetric ion sensors. This new method postulates a direct relationship between the mid point reversible potential, ER, and the logarithm of the electrolyte concentration. In the same way as the other relationships based on the Nernst equation, a positive slope is expected for a cationic exchanging system, and a negative one for an anionic sensor. However, the theoretical slope proposed in this work includes the electron-transfer coefficient, which allows us to explain the slopes frequently reported in the literature non coincident with the ideal value estimated from the Nernst equation: 2.303RT/nF. Also, comments are made on results from other literature with respect to the new equation, and an application of this method to PPy/DBS films as a cation sensor is carried out.