<p>Sensitive and selective sensing of nitrate and phosphate ions in aquatic environments is critical as their roles in eutrophication and potential hazards due to industrial and agricultural pollution. In this study, we repurpose a copper–glycinate coordination complex obtained as a by-product of routine instructional laboratory synthesis and evaluate its applicability as a low-cost electrochemical sensing material. Metal–ligand coordination was confirmed by FTIR spectroscopy showing characteristic Cu–N and Cu–O stretching bands as well as by UV-visible spectroscopy. The modified electrode was further characterised electrochemically and its sensing performance was optimised using cyclic voltammetry. Distinct redox changes with a diffusion-controlled process correlate with a well-defined linear relationship between peak current and nitrate concentration. Under optimised conditions, the sensor demonstrated a limit of detection of 0.175 µM for nitrate along with a broad linear response range. In presence of phosphate, a linear response with minor interference is observed, yet nitrate detection remained selective. This approach highlights the potential of repurposed coordination complexes as a promising, cost-effective sensor for real-time nitrate monitoring in environmental monitoring and contributes to sustainable laboratory practices by upcycling instructional experiment residues.</p> Graphical Abstract <p></p>