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

Bisulfite (HSO3-) and sulfite (SO32-) 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 HSO3-/SO32- detection by coupling 1,4-dimethylquinolinium with 3-quinolinium carboxaldehyde for the first time. The probe DQ showed high selectivity for HSO3- 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 HSO3-. Under the optimized conditions, the far-red fluorescence intensity was linear to the concentrations of HSO3- 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 HSO3- on paper strips, real sample including vermicelli and sugar and image HSO3- in living cells, which indicated that probe DQ has potential application in food samples and living systems.