Determination of hypochlorite and bisulfite in water by bifunctional colorimetric sensor based on octupolar conjugated merocyanine dyes

Abstract

In this study, we developed a bifunctional colorimetric fluorescent sensor based on three merocyanine structures for the detection of hypochlorite (ClO−) and bisulfite (HSO3−). In MeOH solution and under special conditions, this sensor shows high selectivity on fluorescence and UV–Vis spectra for the detection of ClO− and HSO3−, respectively. The sensor solution exhibits a strong red fluorescence emission at 638 nm, which was quenched and the blue color turned to purple pink rapidly upon the addition of ClO−. The mechanism of the detection of ClO− was confirmed via ESI-MS that the CC groups were induced to produce ethylene oxide and ethylene glycol derivatives by hypochlorite. The fluorescence emission at 638 nm in the concentration range of ClO− from 0 to 24 μM showed a good linear relationship (R2 = 0.9919), and the LOD of the sensor for ClO− was 0.42 μM. Interestingly, the sensor can also detect HSO3− in acid condition (pH less than 7.4). The blue shift of UV–Vis spectra of the solution of sensor were observed after addition of HSO3− and irradiation with visible light for about 4 min. The HSO3− concentration showed a good linear relationship (R2 = 0.9987) at 275 nm in the range of 12–42 μM, and thus its LOD was calculated to be 1.14 μM. Finally, the sensor has important value for detecting ClO− and HSO3− in tap water and lake water.