What can go wrong with working electrodes? Surface Contamination, Electrode Fouling, and Their Consequences in Voltammetric Analysis

The performance of voltammetric methods strongly depends on the physicochemical properties, cleanliness, and stability of the working electrode surface. Although working electrodes are commonly considered reliable platforms for electrochemical measurements, numerous surface-related processes can significantly compromise their analytical performance, often without being immediately recognized by the experimenter. This contribution provides a comprehensive overview of the major factors responsible for electrode surface contamination, fouling, and deterioration, with particular emphasis on carbon-based, gold, platinum, and screen-printed electrodes. Special attention is given to the adsorption of organic molecules, proteins, thiols, and inorganic anions, as well as the formation of metallic deposits, surface alloys, oxide layers, and insoluble precipitates. Additional complications arise from gas bubble adhesion, mechanical damage, electrochemical corrosion, surface reconstruction, and progressive electrode ageing. In screen-printed electrodes, evaporation of sample droplets, accumulation of nonvolatile residues, and deposition of heavy metals can further modify the effective electrode surface and compromise measurement reproducibility. These processes may alter electron-transfer kinetics, suppress or distort voltammetric peaks, increase background currents, shift peak potentials, and ultimately lead to inaccurate quantitative interpretations. Particular emphasis is placed on the fact that electrode fouling is not always manifested by a simple decrease in current; in certain cases, surface modification may produce unexpected signal enhancement, additional voltammetric peaks, or misleading indications of electrocatalytic activity. Practical approaches for recognizing, preventing, and minimizing these effects are discussed, including appropriate electrode cleaning, electrochemical conditioning, careful selection of supporting electrolytes, and systematic monitoring of electrode reproducibility. Understanding these frequently overlooked limitations is essential for obtaining reliable electrochemical data, particularly in the analysis of complex biological and environmental samples.