Exploring the Effect of Electrode Material on the Electrical Impedance of Liquid Samples

Using a bipolar electrode configuration to collect impedance measurements of a liquid sample captures contributions from the electrode/liquid interface, the liquid, and the instrument used for the measurements. To understand how the selection of electrode material can impact the measured electrical impedance of liquids in this configuration, three liquids (distilled water, ethanol, and citric acid) were measured with three types of electrode materials (copper, gold, and platinum). To facilitate comparisons of the experimental data, a fractional-order equivalent circuit model was used to represent this data and reduce its dimensionality. For each liquid, impedance measurements using the different electrodes had different absolute values and fractional-order representations supporting that electrode material does effect the collected measurements of these types of liquids. This is an important consideration when comparing the electrical impedance of similar liquids measured in similar configurations (e.g. bipolar setup) but with variations in electrode material.