Detection of environmentally hazardous hypochlorite in pure water with a novel fluorescent chemosensor: Application to water samples, commercial disinfectants, test strips, and zebrafish

With the increasing use of chlorinated disinfectants or bleaches such as sodium hypochlorite in the coronavirus disease 2019 (COVID-19) pandemic, the effectual detection of toxic hypochlorite is very important. In this study, a novel hydrazide-based fluorescence chemosensor DHT-Cl ((E)-2-(2-(3,5-dichloro-2-hydroxybenzylidene)hydrazinyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride) was synthesized. DHT-Cl could selectively detect environmentally hazardous hypochlorite in pure water through a fluorescence turn-off process. The detection limit for hypochlorite was determined to be 0.57 μM. DHT-Cl can monitor hypochlorite with little interference even in the presence of other analytes. Practically, DHT-Cl detected hypochlorite in water samples, commercial disinfectants, test strips, and living zebrafish. The hypochlorite detection mechanism through cleavage of the C[dbnd]N bond was illustrated by ¹H NMR spectroscopy titration, ESI-mass spectrometry and quantum calculations.