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 (HSO3-) 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 HSO3- detection was of great significance to human health. In this work, a new reaction-based ratiometric fluorescent probe KQ-SO2 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[e]indolium moiety and a carbazole group through a condensation reaction resulted in KQ-SO2, 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-SO2 has been successfully applied for the detection of HSO3- in tap water, real food samples, onion tissues, and zebrafish with satisfactory results. We predict that KQ-SO2 could be used as a powerful tool to reveal the relationship between HSO3- and the human health.