Comparative Evaluation and Reproducibility Assessment of Commercial Screen-Printed Carbon Electrodes for Electroanalytical Applications

Commercial carbon-based screen-printed electrodes (SPEs) are extensively used across a wide range of fields, particularly as versatile platforms for subsequent modification with nanomaterials, biomolecules, and complex functional systems. These modifications enable the development of sensors for diverse applications, including environmental monitoring, clinical diagnostics, point-of-care testing, quality control, and food safety analysis. Despite their widespread use, the specific type of commercial electrode selected is often treated as a secondary factor, although its influence on analytical performance should not be underestimated. In this study, six commercially available carbon-based SPEs were investigated by comparing their electrochemical behaviour using cyclic voltammetry and electrochemical impedance spectroscopy. Both outer- and inner-sphere redox probes were employed to provide complementary insights into electrochemical performances. These electrochemical measurements were combined with wettability and surface roughness characterization to better understand how variations in surface heterogeneity contribute to differences in electrochemical reversibility, mass transport regime, and current intensity. Furthermore, the results highlight that electrode performance variability arises not only between different commercial SPEs, but also from repeated measurements on the same electrode and from changes in experimental configuration, such as conventional bulk solution measurements compared to droplet-based setups, emphasizing the critical role of testing conditions.