Disposable electrochemical sensor modified with gold nanostructures for rapid and eco-friendly nitrit

Abstract

Nitrite monitoring in drinking water is essential for public health due to its toxicological risks. Despite its relevance, the official Griess-based spectrophotometric method presents limitations such as bulky instrumentation, sample instability, and the need for centralized analysis. Electrochemical sensors offer a promising alternative for on-site and real-time detection; however, few have reached the market due to complex fabrication and insufficient analytical validation. In this work, we present a miniaturized and disposable electrochemical sensor for nitrite quantification in tap water. Gold nanostructures were electrodeposited onto screen-printed carbon electrodes via a one-step modification. As a key distinguishing feature, we conducted the full analytical validation directly in tap water — from calibration curve construction to all figures of merit, addressing matrix effects through the standard addition method. The sensor exhibited excellent linearity from 1 to 24 μmol L− 1 , with a limit of detection of 0.72 μmol L− 1 and a limit of quantification of 2.18 μmol L− 1 , both below the maximum levels established by the World Health Organization (WHO), Environmental Protection Agency (EPA), and Brazilian National Environment Council (CONAMA). For the first time, intermediate precision was evaluated using a nested design that considered different days, electrodes, and replicates. The results showed minimal variation between electrodes and days, while repeatability represented the main source of variability — an issue inherently mitigated by the single-use nature of the electrodes. Accuracy ranged from 92 % to 98 %, and no interference was observed from common contaminants, confirming the sensor’s selectivity. These results, along with a high Blue Applicability Grade Index (BAGI) score of 70.0, underscore the sensor’s reliability for nitrite detection in real matrices and its strong potential for commercial application, bridging the gap between academic research and real-world implementation.