Enhancing Square Wave Voltammetry Measurements via Electrochemical Analysis of the Non-Faradaic Potential Window.

Abstract

Square wave voltammetry (SWV) is most commonly used to enhance electroanalytical current signals of a redox analyte of interest. The SWV is typically recorded in a potential region where both non-faradaic and faradaic currents are collected; however, only data in the faradaic region are analyzed. In this article, we show how by collecting the full current-time ( i- t) data, arising from the SWV potential pulse sequence, and analyzing in the region of the potential scan where non-faradaic currents arise, further analytical information can be collected, over short time periods (typically seconds). Importantly, we show how information on solution resistance, R (and solution conductivity), and double layer capacitance, C, can be extracted from this data, without the need to conduct further electrochemical experiments, such as electrochemical impedance spectroscopy or independent solution conductivity measurements. Knowledge of the latter is important for measurements in real world samples, where the electrolyte concentration is unknown. We show how SWV measurements of electrode capacitance with repeat SWV scans can also be used to determine whether a changing faradaic SWV signal is due to electrode fouling or changing analyte concentration. Finally, knowledge of both parameters ( RC) is essential for optimization of the SWV parameters, such that the faradaic SWV signal is truly free from non-faradaic contributions.