Nanoporous Gold Thin-Film Microelectrode for Nitrite Detection in Microalgae-Growing Media

Nitrite indicates nitrogen availability in aquatic ecosystems, with primary productivity and ecological balance implications. However, excessive nitrite accumulation poses significant risks to aquatic life, necessitating reliable detection methods. Electrochemical approaches offer flexibility and adaptability crucial for varied research needs, and nanoporous electrode surface modification emerges as a promising strategy to enhance sensitivity and precision in nitrite detection. In this study, a sensitive sensor is developed utilizing gold microelectrodes modified with nanoporous gold to detect nitrite. At optimized conditions, the sensor has a linear response (R² = 0.994) in the nitrite concentration range from 50 to 1 mmol L⁻¹ and a detection limit of 8.9 nmol L⁻¹ following the 3σ/s method. The results show that the proposed sensor can perform electrochemical detection with high repeatability (relative standard deviation (RSD) = 2%, n = 7) and reproducibility (RSD = 2%, n = 8). The concentration of nitrite in tap water and microalgae-growing media samples was determined, and the results agreed with those from the Griess method. These findings challenge conventional surface area, sensitivity, and detection limit assumptions, highlighting the nuanced relationship between electrode surface morphology and detection limit and presenting some evidence that the highest sensitivity does not always reflect on the lowest detection limit.