A fluorescent turn-on probe based on benzo[e]indolium for bisulfite through 1,4-addition reaction

A new fluorescent turn-on probe for HSO3− bearing a benzo[e]indolium moiety was developed. The HSO3− undergoes 1,4-addition reaction with the C-4 atom in the ethylene group, resulting in a prominent fluorescence enhancement and a fluorescent color change. The reaction could be completed in 1 min in PBS buffer, and displayed a high selectivity and sensitivity for HSO3− against other anions, including CN−. Moreover, the practical value of the probe was confirmed by application to detect the level of HSO3− in sugar samples.