Development of a Photolithographed Ultramicroelectrode Array for Sampled Current Voltammetry: Application to Diclofenac as an Electrode-Passivating Analyte

Sampled-current voltammetry (SCV) is a particularly interesting analytical method. It represents a valuable alternative to linear sweep voltammetry (LSV) using a rotating disk electrode, which is commonly employed for evaluating the electrocatalytic activity of materials. The method involved applying a different potential to each electrode in the array, thereby renewing both the solution and the electrode surface throughout the analysis. This electrochemical analysis concept, referred to as electrode array for sampled-current voltammetry (EASCV), was applied to the analysis of compounds that poison the electrode surface, such as phenol derivatives. Although this method provided higher sensitivity compared to LSV, a high signal-to-noise ratio resulted in similar limits of detection (LOD). In this work, we report the fabrication of arrays composed of several ultramicroelectrodes using photolithography. A life cycle assessment was conducted to quantify the environmental impacts associated with the array manufacturing. The arrays were characterized by scanning electron microscopy (SEM), scanning electrochemical microscopy (SECM), and cyclic voltammetry (CV). Using potassium ferrocyanide as a model compound, we demonstrated the advantages of UME arrays in reducing the signal-to-noise ratio and achieving LODs as low as 3 μM, which is ten times lower than those obtained with a macroelectrode, while maintaining higher sensitivities than those achieved with conventional LSV analysis. The method was also successfully applied to the analysis of diclofenac, which is known to poison the electrode surface during oxidative analysis, with performance comparable to that of ferrocyanide.