Rational Development of a New Reaction-Based Ratiometric Fluorescent Probe with a Large Stokes Shift for Selective Detection of Bisulfite in Tap Water, Real Food Samples, Onion Tissues, and Zebrafish.

Bisulfite (HSO) is usually widely added to tap water and food because it has antibacterial, bleaching, and antioxidant effects. However, its abnormal addition would cause a series of serious diseases related to it. Therefore, development of an effective method for HSO detection was of great significance to human health. In this work, a new reaction-based ratiometric fluorescent probe KQ-SO was rationally designed, which could be used for the highly selective detection of HSO3 in tap water, real food samples, onion tissues, and zebrafish. Specifically, a positively charged benzo[]indolium moiety and a carbazole group through a condensation reaction resulted in KQ-SO, which displayed two well-resolved emission bands separated by 225 nm, fast response (1 min), and high selectivity and sensitivity toward HSO3 upon undergoing the Michael addition reaction, as well as low cytotoxicity in vitro. In addition, KQ-SO has been successfully applied for the detection of HSO in tap water, real food samples, onion tissues, and zebrafish with satisfactory results. We predict that KQ-SO could be used as a powerful tool to reveal the relationship between HSO3 and the human health.