Amperometric Signal Generation by Self-Doped Polyanilines for Ion-Selective Electrodes

Abstract

Flow injection amperometry provides an opportunity to avoid common drawbacks of classical potentiometry for solid-contact ion-selective electrodes. The current is generated by solid-contact in course of the polymer chain recharging in response to an excess of cations or anions in the polymer film. Cations cause cathodic peaks on the chronoamperogram, while anions result in anodic peaks. For polyaniline with negatively charged substituents, a response to cations is observed, whereas the presence of uncharged ones results in anion detection. Moreover, in the case of the protonated –SO₃H group, this compensating current is an order of magnitude lower than that for the deprotonated one. For electroactive self-doped polyanilines, the maximal amperometric signal is achieved at the working potential within the electroactivity range. The proposed constant potential amperometric approach was validated by the successful analysis of human serum with a Na⁺-selective electrode based on polyaniline.