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 addit...