Dual validation of nitrite in water samples through combining bromocresol green with colorimetric and electrochemical analysis

Nitrite (NO 2 − ) is a potential contaminant in water samples, capable of causing adverse effects on human health. Therefore, it is essential to develop effective, rapid, and portable methods for in situ monitoring. In this context, colorimetric methods and electrochemical sensors stand out for their low cost, operational simplicity, and ability to achieve accurate results in environmental sample analyses. To further enhance user confidence, this study presents a combined approach for nitrite determination in water samples, integrating colorimetric detection using bromocresol green as a reagent with electrochemical analysis via screen-printed carbon electrodes. The proposed method demonstrated linear ranges between 12 and 400 μmol L −1 before the colorimetric reaction and 50–400 μmol L −1 afterwards, with excellent limits of detection of 0.36 μmol L −1 and 38 μmol L −1 for each step, respectively. Excellent selectivity with both methods was achieved, even in the presence of potential interferences, along with recoveries close to 100 % in real water samples. Furthermore, this approach aligns with green chemistry principles by minimising waste and avoiding complex electrode modifications. This combined strategy demonstrates efficient, validated analytical performance, making it a reliable and practical solution for monitoring nitrite levels in environmental water samples. • Combined colorimetric and electroanalytical nitrite sensing in water samples. • Rapid and simple determination of nitrite without complex electrode modifications. • Excellent analytical performance with a LOD of 0.36 μmol L −1 and recoveries of ~100 %. • High sensitivity and selectivity in the presence of potential interferents present in environmental waters. • Robust internal methodological validation for real field applications.