Redox-amplified pyrolytic glassy carbon sensor for ultrasensitive simultaneous detection of nitrate and nitrite

This work reports a novel four-electrode electrochemical sensor based on pyrolyzed glassy carbon microstructures for ultrasensitive and simultaneous detection of nitrate and nitrite. Unlike conventional three-electrode sensors, this sensor integrates a copper nanoparticle (CuNP)-modified working electrode and a gold nanoparticle (AuNP)-modified auxiliary oxidation electrode within a microfluidic platform, establishing an innovative redox amplification mechanism that markedly boosts detection sensitivity. Through systematic optimization of electrodeposition and operational parameters, the device delivers highly reproducible and selective responses. Notably, the four-electrode configuration achieves a 2 ppb detection limit for nitrate and a 100 ppb detection limit for nitrite, representing a two-order-of-magnitude improvement over standard architectures. Furthermore, simultaneous quantification of nitrate and nitrite is realized by resolving distinct oxidation potentials. The sensor's integrated design, amplification strategy, and microfluidic compatibility collectively enable a low-cost, reusable, and high-performance platform for environmental monitoring of nitrogen contaminants.