A coumarin-based fluorescence turn-on probe for specific detection of HSO3- in food, traditional Chinese medicine, and biological samples.

Sulfite (HSO3-) is a common additive in food and traditional Chinese medicinal materials processing, yet overdosing endangers health, demanding an efficient detection method. Herein, we chosed the coumarin derivative as the fluorophore and incorporated electron-withdrawing groups, 2-thiobarbituric acid and barbituric acid, to synthesize fluorescent probes CADS and CADT. Both probes gave a pronounced HSO3- response in HEPES: cyan fluorescence switched on and the color changing from purple/pale purple to yellow. By comparison, CADS outperformed with 40 s response, pH 4-8 tolerance, superior photostability and anti-interference. Spectroscopic characterization experiment and quantum chemical calculation results indicated that the probe specifically identified HSO3- through a nucleophilic addition reaction and emitted fluorescence by inhibiting the internal conversion (IC) process. Furthermore, CADS was successfully applied to the quantitative detection of HSO3- in food and Chinese medicinal material samples and enabled fluorescence imaging of endogenous and exogenous HSO3- in MCF-7 cells and zebrafish.