A FRET-based ratiometric fluorescent probe for sensing bisulfite/sulfite and viscosity and its applications in food, water samples and test strips

A FRET-based ratiometric dual-response fluorescent probe, CQI, constructed by combining quinolinium-indole as the acceptor and coumarin as the donor, was developed for sensing HSO3-/SO32- and viscosity. After the interaction of probe CQI with the analyte, we achieved a green channel for the response to HSO3-/SO32- and an orange channel for the response to viscosity. We comprehensively evaluated the ability of CQI to detect SO2 derivatives and viscosity using fluorescence spectroscopy. Probe CQI exhibited a large Stokes shift (196 nm), a high energy transfer efficiency (99.6 %) and a wide detection range (0-250 μM). The fluorescence intensity of the probe increased up to 14-fold with increasing viscosity, and CQI could detect the viscosity of food thickeners. More importantly, probe CQI could not only successfully monitor SO2 derivatives in various food and water samples, but also be prepared as bisulfite test strips.