Graphite-engineered tungsten microneedle sensor for ultra-wide range nitrite detection

This work presents a novel electrochemical sensor based on a graphite-engineered tungsten microneedle electrode (C/TME) for high-performance and ultra-wide linear range detection of nitrite ion (NO₂^-). The sensor leverages the sharp-tip geometry, high electrical conductivity, and mechanical stability of the TME, combined with the large specific surface area and favorable conductivity of graphite, to shorten the measurement time, and improve electrode stability. The graphite engineering promotes NO₂^- adsorption and enrichment, which accelerates electron transfer and enhances sensitivity and selectivity. Importantly, the synergistic effect enables the sensor to achieve ultra wide range (six orders of magnitude) detection of NO₂^-. The C/TME sensor exhibited a wide linear detection range from 5.0 to 105,000.0 μM, a low detection limit of 2.0 μM, and a relative standard deviation (RSD) below 10%. It demonstrated strong anti-interference ability and long-term stability in real-sample testing, including sausage, mariculture water and continuous monitoring of seawater aquaculture water bodies for 15 days. By integrating the structural advantages of TME with the functional properties of graphite, this sensor offers a reliable and portable platform for rapid nitrite quantification in food and environmental applications.