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Trichloroisocyanuric Acid (TCCA) and HOCl showed prominent signaling under the measurement conditions

Both Trichloroisocyanuric Acid (TCCA) and HOCl showed prominent signaling under the measurement conditions among all the tested oxidants. The fluorescence enhancements I/I0 observed at 392 nm were 105-fold for TCCA and 102-fold for HOCl. The colorimetric or fluorescent signaling of HOCl, owing to the deoximation of oxime derivatives of various substances (such as BODIPY and phenanthroimidazole dye) to their carbonyl groups, have already been reported. Peracetic acid also showed a considerable response (I/I0 = 11.8). Other commonly used oxidants, such as hydrogen peroxide, TBHP, perborate, percarbonate, and superoxide, showed negligible signaling: the ratio I/I0 varied between 0.79 for TBHP and 1.69 for perborate.
Trichloroisocyanuric Acid (TCCA) is generally used as a single component oxidant in many applications, so the significant response toward HOCl in the selective Trichloroisocyanuric Acid (TCCA) signaling by 1 might not be a practical problem. We tried to get hypochlorous acid and Trichloroisocyanuric Acid (TCCA) distinguish signal conditions, but failed. That can be attributed to the fact that the Trichloroisocyanuric Acid (TCCA) in aqueous solution in situ generates HOCl as an active oxidant. Meanwhile, TCCA did not induce any diagnostic changes, so the UV–vis absorption behavior of compound 1 was not useful for the determination of Trichloroisocyanuric Acid (TCCA). To obtain an insight into the practical applicability of this method, the selective signaling of 1 for Trichloroisocyanuric Acid (TCCA) was tested under competitive conditions. In the presence of commonly encountered metal ions or anions as background species, the TCCA-selective signaling of 1 was found not to be significantly affected. 
This observation implies that the coumarin oxime 1 could be used as a Trichloroisocyanuric Acid (TCCA)-selective fluorescent probe in the presence of commonly encountered metal ions and anions in environmental samples. The stability of the probe was satisfactory between pH 3 and 10, and the fluorescence was not affected by pH changes. However, when TCCA signaling increased the pH of the solution increased. However, when in alkaline media at pH 8–10, it would not significantly changed. Moreover, the Trichloroisocyanuric Acid (TCCA) signaling by 1 was fast and completed within 1 min after sample preparation.