Nanomolar colorimetric hypochlorite sensor in water.

Hypochlorous acid is present in several biological systems and plays a pivotal role in bioprocesses. The acid also finds application in industrial and synthetic spheres. The ecological toxicity of elevated hypochlorite concentrations in aqueous media has been thoroughly documented. As a consequence, there is a pressing need to develop quantitative and qualitative methods for the detection of hypochlorite in water. In this regard, nanomolar detectable, non-toxic and intensely coloured probes based on commercially available dyes such as Fuchsin basic, Methyl violet, Acid red-1, and Trypan blue have been successfully applied for hypochlorite detection in fully aqueous media. In all of these cases, specific and selective naked eye sensing of hypochlorite was achieved. As a rule of thumb, the addition of hypochlorite to a dye solution results in discoloration. The sensing mechanism follows an oxidative chemodosimetric approach and UV-Vis, as well as NMR titration experiments, support the oxidative cleaving of the molecular framework even in the presence of hypochlorite in trace amount (>1 nM). Furthermore, probes are subjected towards real-sample analysis of daily use water which contains bleaching agent and found to be promising in strip test too. Limits of detection of the dyes Fuchsin basic, Methyl violet, Acid red-1 and Trypan blue are 0.86 nM, 2.97 nM, 2.31 nM and 30 μM respectively. These dyes are promising analytical tools for the detection of hypochlorite.

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