A phenothiazine-based ratiometric fluorescent probe for detecting hypochlorite (ClO−) and its application in foods and water samples

As a significant reactive oxygen species (ROS), ClO⁻ plays versatile roles in daily life and many biological events. However, its abnormal levels are responsible for serious harm to human health. Therefore, it is of crucial interest to develop effective methods for detecting ClO⁻ in foods and living organisms. In this work, a novel fluorescent probe ethyl 2-(3-formyl-2-methoxy-10H-phenothiazin-10-yl)acetate (PEA) for detecting ClO⁻ was presented. It shows the merits of rapid ratiometric response (within 10 s), high selectivity and very large Stokes shift (190 nm). The detection limit of PEA for ClO⁻ was determined to be 0.47 μM. We not only successfully prepared paper test strips for efficient qualitative naked eye ClO⁻ detection, but also demonstrated its potential for the valid detection of ClO⁻ in natural water samples, beverages and foods. Furthermore, the probe PEA was also applied to the fluorescence imaging of ClO⁻ in onion epidermal cells.