Published July 1, 2020 | Version Published
Journal article Open

Quantitative analysis of redox-inactive ions by AC voltammetry at a polarized interface between two immiscible electrolyte solutions

  • 1. Departamento De Química, Facultad De Ciencias, Universidad Nacional De Colombia, Cra 30 # 45-03, Edificio 451, Bogotá, Colombia
  • 2. The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick (UL), Limerick V94 T9PX, Ireland


The interface between two immiscible electrolyte solutions (ITIES) is ideally suited to detect redox-inactive ions by their ion transfer. Such electroanalysis, based on the Nernst-Donnan equation, has been predominantly carried out by amperometry, cyclic or differential pulse voltammetry. Here, we introduce a new electroanalytical method based on AC voltammetry with inherent advantages over traditional approaches such as avoidance of positive feedback iR compensation, a major issue for liquid|liquid electrochemical cells containing resistive organic media and interfacial areas in the cm2 and mm2 range. A theoretical background outlining the generation of the analytical signal is provided and based on extracting the component that depends on the Warburg impedance from the total impedance. The quantitative detection of a series of model redox-inactive tetraalkylammonium cations is demonstrated, with evidence provided of the transient adsorption of these cations at the interface during the course of ion transfer. As ion transfer is diffusion limited, by changing the voltage excitation frequency during AC voltammetry, the intensity of the Faradaic response can be enhanced at low frequencies (1 Hz) or made to disappear completely at higher frequencies (99 Hz). The latter produces an AC voltammogram equivalent to a “blank” measurement in the absence of analyte and is ideal for background subtraction. Major opportunities therefore exist for the sensitive detection of ionic analyte when a “blank” measurement in the absence of analyte is impossible. This approach is particularly useful to deconvolute signals related to reversible electrochemical reactions from those due to irreversible processes, which do not give AC signals.


M.F.S.-H. acknowledges the "Universidad Nacional de Colombia" for allowing his sabbatical leave.



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Designing Reactive Functionalised Soft Interfaces _ Self-healing soft materials for solar energy conversion, energy storage, and sustainable low cost hydrogen production 13/SIRG/2137
Science Foundation Ireland
SOFT-PHOTOCONVERSION – Solar Energy Conversion without Solid State Architectures: Pushing the Boundaries of Photoconversion Efficiencies at Self-healing Photosensitiser Functionalised Soft Interfaces 716792
European Commission