Advantages of Amperometric Readout Mode of Ion‐selective Electrodes under Potentiostatic Conditions

Abstract

Amperometric responses of all‐solid‐state ion‐selective electrodes, recorded under potentiostatic conditions, were studied on example of potassium‐selective sensors with polypyrrole solid contact, at potential corresponding to reduction of the solid contact material and accompanying transfer of potassium ions across the membrane. Selective and stable in time linear dependences of current vs. logarithm of analyte concentration were recorded, resulting from high membrane resistance and changing membrane potential. The influence of experimental parameters as applied potential or thickness of the membrane was discussed. Advantages of the amperometric mode compared to potentiometric one relate to possibility of tailoring analytical parameters (sensitivity, magnitude of the signal) as well as over one order of magnitude decrease of the detection limit. The latter effect is achieved due to externally forced incorporation of potassium ions from the solution to the membrane, compensating their spontaneous release to the sample solution. A method of experimental setup simplification was proposed, with application of two‐electrode system, which can be used in the absence of external polarization source. The required driving force for the current flow was assured by spontaneous oxidation process occurring at the second electrode, coupled with reduction of the solid contact material of the ion‐selective electrode. In this case also stable in time calibration plots can be recorded.

Potentiometric Sensing

“…Jaworska et al. explored the amperometric responses of solid-state ISEs, recorded under potentiostatic conditions . They used potassium-selective electrodes with polypyrrole (PPY) as an ion-to-electron transducer for their study.…”

“…Jaworska et al explored the amperometric responses of solid-state ISEs, recorded under potentiostatic conditions. 44 They used potassium-selective electrodes with polypyrrole (PPY) as an ion-to-electron transducer for their study. The potential value was chosen to force the reduction of PPY and transfer of potassium ions across the membrane.…”

Ionophore-Based Ion-Selective Electrodes in Non-Zero Current Modes: Mechanistic Studies and the Possibilities of the Analytical Application

“…From the sensitivity viewpoint the coulometric mode is by far superior to the classical potentiometric readout where the sensitivity of the ISE response to species is limited by the value of the Nernst factor On the other hand, coulometric measurements require a relatively long time to accumulate the signal. From this point of view, the use of the current value instead of that of charge, as the analytical signal, may be advantageous [79]. However, a change of the solution composition requires time.…”

Constant Potential Coulometric Measurements with Ca2+-Selective Electrode: Analysis Using Calibration Plot vs. Analysis Using the Charge Curve Fitting

“…The constant potential coulometry method invented in the Bobacka’s group opened new opportunities for the use of ion-selective electrodes (ISEs) [ 1 , 2 , 3 ]. Originally, the features of the method were studied with K + -selective ISEs as a model system [ 1 , 2 , 3 , 4 ]. Further studies showed that this method can be used for quantification of divalent cations Ca 2+ , Pb 2+ , and Cu 2+ [ 5 , 6 , 7 ], and NO 3 − , SO 4 2− , and ClO 4 − anions [ 8 , 9 ].…”