A liquid-junction-free reference electrode based on a PEDOT solid-contact and ionogel capping membrane

Abstract

Liquid-junction-free reference electrodes have been prepared on screen printed substrates using poly-3,4-ethylenedioxythiophene (PEDOT) as solid-contact and novel ionogels as capping membrane. The chemico-physical properties of the PEDOT layer were tuned by changing the electropolymerization media and the electrodeposition technique. Electrodepositing PEDOT films potentiostatically or potentiodynamically were found to have a significant impact on the stability of the electrodes during the conditioning step. Optimization of the capping membrane formulation, e.g., acrylate monomers, ionic liquid, cross-linkers and photo-initiators, produced electrodes with properties almost equivalent with a commercial reference electrode. Thus, calibration plots of Na(+) ion-selective electrodes against the optimized solid-contact ionogel reference electrodes (SCI-REs) or against a double-liquid junction Ag/AgCl electrode did not present any significant difference. Such SCI-REs may provide an effective route to the generation of future low-cost components for potentiometric sensing strips.

A potentiometric disposable sensor strip for measuring pH in saliva

“…The solid-contact ionogel reference electrodes (solid-contact-REs) were prepared as reported elsewhere [26] using the silver-free screen printed substrates. In summary, the solid contact was a PEDOT layer electrochemically grown on the carbon electrodes from a 0.…”

“…In fact, when the concentrations of K + and Na + change over two orders of magnitude, i.e., from 1 mM to 0.1 M, the potential of these solid-contact reference electrodes increases by ca. 4-6 mV and 10-15 mV, respectively, against a commercial double-junction reference electrode [26]. In saliva, sodium and potassium levels significantly depend on the area and sampling method, but their concentrations range are always within 1-98 mM and 10-80 mM, respectively [28].…”

Simultaneous Determination of Na+, K+, Ca2+, Mg2+and Cl−in Unstimulated and Stimulated Human Saliva Using All Solid State Multisensor Platform

“…Another example is the all‐solid‐state reference electrode with heterogeneous membrane, which was made using silver nanoparticles . One of the most interesting ideas, which has a large potential application is the use of Ag/AgCl electrode dipped in a KCl dispersed in the polymer .…”

Evaluation of Ionic Liquids Based on Amino Acid Anions for Use in Liquid‐junction Free Reference Electrodes

“…In the Ag/AgCl electrode was covered with the gel‐like IL in order to make it insensitive to the solution composition and in addition to avoid using inner solution. For the same purpose, ionogel instead of a polymeric capping membrane was proposed in to cover the solid‐contact reference electrode. Lately the ILs were utilized directly in the polymeric electrode membranes .…”

“…Despite a lot of promising results, the verification of the reference properties of the IL‐based membranes in electrolyte solutions lacks a systematic approach. In most of the works, one or two, a maximum of three, different electrolytes are tested, and often systematic and significant dependence of the RE potential on the electrolyte concentration is considered acceptable . All these issues, and many more, are nicely reviewed and addressed in .…”