A colorimetric and far-red fluorescent probe for rapid detection of bisulfite/sulfite in full water-soluble based on biquinolinium and its applications.

Bisulfite (HSO) and sulfite (SO) are involved in numerous physiological processes of living systems. However, high levels of these substances are often correlated to many diseases. Herein, we designed and synthesized a simple full water-soluble colorimetric and far-red fluorescent probe (E)-1-methyl-4-(2-(1-methylquinolin-1-ium-3-yl)vinyl)quinolin-1-ium iodide trifluoromethanesulfonate (DQ) for HSO/SO detection by coupling 1,4-dimethylquinolinium with 3-quinolinium carboxaldehyde for the first time. The probe DQ showed high selectivity for HSO detection via a 1,4-nucleophilic addition reaction with distinct color changes from colorless to purple-red and remarkable far-red fluorescence enhancement in pure aqueous solutions. Specifically, the probe displayed a fast response (<15 s) for bisulfite, which renders it suitable for real time detection of HSO. Under the optimized conditions, the far-red fluorescence intensity was linear to the concentrations of HSO in the range from 0 to 25 μM and the detection limit was as low as 0.11 μM. Additionally, the probe could be applied to sense HSO on paper strips, real sample including vermicelli and sugar and image HSO in living cells, which indicated that probe DQ has potential application in food samples and living systems.