A simple and highly selective 1,2,4,5-tetrazine-based colorimetric probe for HSO ion recognition in food.

A series of 3,6-bis-substituted-1,2,4,5-tetrazine-based colorimetric probes has been developed in good yields that exhibits highly selective and sensitive colorimetric recognition of HSO in aqueous solution. The color of the solution containing colorimetric probes changed markedly from orange to colorless, upon the addition of HSO . Quantification of the absorption titration analysis shows that the detection limit of 3,6-bis(2-aminoethylamino)-1,2,4,5-tetrazine (2a) for HSO was 3.8 μM. It was noted that 3,6-bis-substituted-1,2,4,5-tetrazine-based colorimetric probes have a specific response toward HSO without interference from other 17 different anions and 16 common cations. A plausible mechanism was proposed by high-resolution mass spectroscopy analysis and NMR spectrometry analysis, involving the nucleophilic reaction of a bisulfite anion with the tetrazine ring and free radical rearrangement of ·SOH. Moreover, probes 2a-2c possessed applicability for sensing bisulfite in actual food samples. Therefore, the present work established a novel strategy for investigating bisulfite in food or other products.