Exploration of a new approach for detection of nitrite with hydroxyl radical fluorescence probe in aqueous solutions

Nitrite (NO₂^-) has been widely recognized by the international community as an important substance affecting water quality safety and human health, and the detection of NO₂^- has always been a hot topic for researchers. Fluorescent probe method is an emerging and ideal way for detecting NO₂^-. Due to the high dependence of the reported reactive NO₂^- fluorescent probes on strong acidic systems, using the idea of photochemistry, a fluorescence analysis method for detecting NO₂^- was proposed in this work to change the necessity of strong acidic solutions in probe detection process. A 365 nm UV-LED lamp was used to irradiate NO₂^- in aqueous solution to convert it into hydroxyl radicals (HO·), and capture the photodegradation product of NO₂^- using coumarin-3-carboxylic acid as probe 3-CCA that can react with HO· to generate only one type of strong fluorescent substance. This probe has excellent photostability, selectivity, and anti-interference ability, and can realize the quantitative detection of NO₂^- (0-15 μM) in pure aqueous solution with pH of 7.4. In addition, its application in actual water samples is also satisfactory, with a recovery rate of (85.91 %-107.30 %). Importantly, we hope that this photolysis strategy can open up the novel thinking to develop suitable fluorescent probes for the analysis and detection of some hardly detected analytes.