Potentiometric Phosphate Ion Sensor Based on Electrochemically Modified All-Solid-State Copper Electrode for Phosphate Ions’ Detection in Real Water

The importance of phosphates has sparked researchers’ considerable interest in the electrochemical detection of phosphates within aqueous solutions in recent years. In this study, we present a novel all-solid-state phosphate ion-selective electrode (ISE) that integrates copper, copper nanoparticles, and copper phosphate. By modifying the copper substrate of the electrode with a copper nanoparticle film and creating a lamellar copper phosphate film through electrochemical treatment, we significantly enhanced the electrode’s electron transfer efficiency. This microstructure with large specific surface area markedly improved the electrode’s responsiveness to the targeted ions by accelerating the achievement of chemical equilibrium on the electrode surface, thereby boosting its sensitivity and stability. The newly developed electrode was capable of detecting phosphate ions in solutions with a pH range from 6 to 11 and performed optimally in neutral solutions at pH 7, following Nernst principle, with a detection limit of 1 × 10−6 M. The electrode exhibited a short response time of less than 10 s with significant reproducibility, stability, longevity—maintaining functionality for more than two months. It also displayed good selectivity as the electrochemical equilibrium was not influenced by up to 1 mM of potential competing species like HCO3−, NO3−, Cl− and SO42−. We compared the detection results of current phosphate ion sensor and conventional determination methods for phosphate content in natural lake and aquaculture water samples, with a detection discrepancy of about 10% (RSD). Considering all feasible performance characteristics combined with its low cost, simple manufacture and portability, the sensor provides a new possibility for rapid, reliable, and long-term real-time in situ detection of phosphates.