A fluorescein-based highly specific colorimetric and fluorescent probe for hypochlorites in aqueous solution and its application in tap water

A fluorescein derivative, 2-pyridylaldehyde fluorescein hydrazone (FHP), was developed for detection of hypochlorites. This probe functioned by oxidizing Cu+ to Cu2+ to form a Cu2+ complex, which produced colorimetric and fluorescent signals that were monitored by ultraviolet–visible and fluorescence spectrophotometry, respectively. Other common anions, including F−, Cl−, ClO3−, NO2−, CN−, S2−, SCN−, P2O74−, AcO−, CO32−, SO42−, ClO4−, did not interfere with the hypochlorite detection, and hypochlorites could be detected at low micromolar levels in aqueous solutions. The color change on reaction with hypochlorites was rapid and visible to the naked eye. The sensor could be applied to the detection of hypochlorites tap water.