Selective fluorescence signaling of hypochlorite in tap water by oxidative hydrolysis of sulfonhydrazone

- Fluorogenic type hypochlorite-selective probe was developed for tap water analysis.
- Signaling was based on hypochlorite-triggered oxidative hydrolysis of sulfonhydrazone.
- Selective sensing over other oxidants was possible with a detection limit of 20 nM.
- The probe could conveniently determine hypochlorites in tap water using a smartphone.

A new hypochlorite-selective fluorescence signaling probe based on the sulfonhydrazone of 2-acetyl-6-methoxynaphthalene was investigated. The probe was easily prepared by the simple one-step reaction of 2-acetyl-6-methoxynaphthalene with p-toluenesulfonylhydrazide. The probe exhibited off/on-type fluorescence signaling behavior toward hypochlorite in aqueous solution via hypochlorite-triggered oxidative hydrolysis of the sulfonhydrazone to yield strongly fluorescent 2-acetyl-6-methoxynaphthalene. Selective hypochlorite signaling over other common oxidants with a large fluorescence enhancement (76-fold) was possible, with a detection limit of 2.0 × 10−8 M. Hypochlorite signaling was not affected by the presence of other common metal ions or representative anions. As a practical application, the methoxyacetylnaphthalene sulfonhydrazone probe was used to determine hypochlorite levels in a tap water sample using a standard smartphone as the detection tool.

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