A Current Averaging Strategy for Maximizing Analyte and Minimizing Redox Interference Signals with Square Wave Voltammetry

Square wave voltammetry (SWV) is commonly used in electroanalytical applications to enhance analyte faradaic signals and minimize nonfaradaic processes. However, little attention is given as to how best use SWV to minimize faradaic interference signals that arise from redox species present in solution that have redox potentials that convolute with that of the analyte. In conventional SWV, a series of current–time (i–t) transients are collected, and i is averaged over a specified window of each transient (potentiostat dependent). This average i is reported against the electrode potential, E. As the i–t response is governed by the type of electron transfer reaction under investigation, we show how by collecting all i–t data and through judicious choice of the current averaging window, it is possible to enhance the analyte response while at the same time reducing the interferent signal. We look at three different electron transfer reactions, fast electron transfer outer sphere, metal electrodeposition/stripping, and surface-confined proton-coupled electron transfer (PCET) and demonstrate different i–t behaviors in SWV, visually aided by the use of 3D i–t–E plots. In the case of PCET quinone-based voltammetric sensing of pH in the presence of a heavy metal (here Cu²⁺), we show that the use of a much earlier current averaging window (2–10% of the i–t response) results in the pH signal being clearly distinguished from that of the overlapping heavy metal.