Capacitive Model for Coulometric Readout of Ion-Selective Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Analytical Chemistry

Background:

• Solid-contact ion-selective membrane electrodes (SC-ISE) are crucial for ion detection.
• Developing efficient signal transduction mechanisms is key for SC-ISE sensitivity.
• Conducting polymers (CPs) offer promising properties for ion-to-electron transduction.

Purpose of the Study:

• To present a capacitive model for coulometric signal transduction in SC-ISEs.
• To investigate the role of conducting polymers, specifically poly(3,4-ethylenedioxythiophene) (PEDOT), as an intermediate transduction layer.
• To demonstrate the sensor's utility for detecting low anion concentrations.

Main Methods:

• Development and application of a capacitive model for coulometric readout.
• Fabrication of chloride-selective SC-ISEs using PEDOT doped with chloride as the transducer.
• Exploration of varying PEDOT and ion-selective membrane thicknesses, and membrane compositions.
• Evaluation of sensor responses using current-time, charge-time, and charge-chloride activity relationships.

Main Results:

• The capacitive model showed strong correlation with experimental data for chloride-selective SC-ISEs.
• The influence of PEDOT thickness and ion-selective membrane properties on sensor performance was systematically studied.
• Prussian blue was utilized as a sodium capacitor to further validate the transduction layer's function.
• The sensor demonstrated effective monitoring of minute changes in chloride concentration.

Conclusions:

• The developed capacitive model accurately describes coulometric signal transduction in CP-based SC-ISEs.
• Conducting polymers like PEDOT are effective ion-to-electron transducers for anion detection.
• The SC-ISE with coulometric readout is a viable tool for sensitive monitoring of low analyte concentrations.