Fluorimetric Readout of Ion Selective Electrode Signals Operating under Chronopotentiometric Conditions

Abstract

The applicability of emission readout of ion‐selective electrodes, containing fluorimetrically active polyoctylthiophene in the membrane, operating under chronopotentiometric mode was studied. The electrochemical and optical signals were collected in the same experiment and compared. In both modes a change in recorded signal: potential or emission in time was observed while a constant current was applied to the sensor. The recorded signals (chronopotentiometric, fluoro‐chronopotentiometric curves and calculated transition times) were dependent on the concentration of potassium ions. The transition times calculated from electrochemical signals were linearly dependent on the concentration of potassium ions in solution within the range: 0.1–0.7 mM. Optically read transition times were also linearly dependent on concentration within the same range, however, they were shorter than those recorded electrochemically. This difference is attributed to various effects represented by the transition time: concentration increase of reduced form of the conducting polymer in the optical mode or depletion of potassium ions close to the membrane surface, in the electrochemical mode.

Solid‐Contact Ion‐Selective Electrodes Paving the Way for Improved Non‐Zero Current Sensors: A Minireview

“…[73,74] In a recent paper also coupled chronopotentiometric and fluorometric response of ion-selective electrodes with POT transducer under galvanostatic conditions was studied. [75] Both modes were found complementary, the transition time related to optical response was shorter than that obtained from electrochemical mode -in the latter case reactant depletion in the diffusion layer is required, while in optical mode only partial transformation of POT to the neutral, fluorometrically active form, is sufficient.…”

Dual Sensitivity─Potentiometric and Fluorimetric─Ion-Selective Membranes

“…The natural choice of optical transducer to obtain DS-ISM is poly­(octylthiophene). This choice is supported by its well-proven applicability in voltammetric ion sensors, including potentiometric and optical sensors, ,,− and compatibility with ionophores and ion exchangers. − …”