Emission Intensity Readout of Ion-Selective Electrodes Operating under an Electrochemical Trigger

Abstract

We report for the first time on in situ transduction of electrochemical responses of ion-selective electrodes, operating under non-zero-current conditions, to emission change signals. The proposed novel-type PVC-based membrane comprises a dispersed redox and emission active ion-to-electron transducer. The electrochemical trigger applied induces a redox process of the transducer, inducing ion exchange between the membrane and the solution, resulting also in change of its emission spectrum. It is shown that electrochemical signals recorded for ion-selective electrodes operating under voltammetric/coulometric conditions correlate with emission intensity changes recorded in the same experiments. Moreover, the proposed optical readout offers extended linear response range compared to electrical signals recorded in voltammetric or coulometric mode.

Dual Sensitivity─Potentiometric and Fluorimetric─Ion-Selective Membranes

“…As POT is insoluble in the membrane plasticizer, mixing the polymer with the membrane cocktail results ultimately in formation of particulates of the polymer within the PVC membrane phase. 20,21 Thus, the interface between the POT and PVC phase is extended, resulting in a more facile ion exchange. 27 POT particulates in the membrane are isolated from the solution ionic redox species influence, 8 the effect that was an Achilles heel of unmodified POT sensors.…”

“…To prepare a DS-ISM, the POT conducting polymer was added to the PVC phase. As POT is insoluble in the membrane plasticizer, mixing the polymer with the membrane cocktail results ultimately in formation of particulates of the polymer within the PVC membrane phase. , Thus, the interface between the POT and PVC phase is extended, resulting in a more facile ion exchange . POT particulates in the membrane are isolated from the solution ionic redox species influence, the effect that was an Achilles heel of unmodified POT sensors. , Adding POT to the membrane allows control of the amount of polymer present in the phase and eliminates the spontaneous partition of POT (from the transducer layer) to the membrane phase …”

“…A 2.5 cm × 0.8 cm rectangle was cut from carbon fiber paper (carbon fiber paper PTFE treated, AvCarb Material Solutions) and used as a support for receptor layers. For potentiometric sensors, carbon paperconductive trackwas isolated using PTFE adhesive tape as described previously, , leaving an opening of diameter 6 mm for the ion-selective membrane to be applied.…”

“…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. − …”

Spectroelectrochemistry with Ultrathin Ion-Selective Membranes: Three Distinct Ranges for Analytical Sensing

“…In recent years, increasing progress has been made in the research field of ion-selective electrodes (ISEs) based on polymeric ion-selective membranes (ISMs) that are interrogated using dynamic electrochemical techniques. 1 The measurements go beyond the traditional zero-current interrogation in potentiometry to pursue challenging analyses based on calibration-free sensors, 2 titration of confined samples, 3 the improvement of the limit of detection, 4 the simultaneous determination of multiple analytes, 5 high-concentration discrimination, 6 and the extension of the linear range of response, 7 among others. Principally, the use of all-solid-state electrodes based on a conducting polymer as the ion-to-electron transducer material with the ISM on top (i.e., a double-layer design) seems to stand out over other design options.…”