A benzo[e]indole[2,1-b][1,3]benzooxazine derivative as a highly sensitive CN- sensor by means of UV?visible difference spectroscopy

In this study, a benzo[e]indole[2,1-b][1,3]benzooxazine derivative 2-nitro-5a-(2-(2-thiophene)-ethylene)-6,6dimethyl-5a,6-dihydro-12H-benzo[e]indolo[2,1-b][1,3]benzooxazi-ne (TEO) was explored as a sensitive probe for CN-. Unlike conventional spiropyrans that possess a 3H-benzo[e]indole cation and a 4-nitrophenolate anion in the same conjugated structure, TEO enhances the positive charge of the 3H-benzo[e]indole cation, which considerably improves its sensitivity and reaction speed. UV?visible spectrophotometry was used to detect CNwith a detection limit of 0.1 ?M and a rate constant of 0.528s-1. In this study, TEO probe showed high selectivity and sensitivity to CN-. Therefore, this probe allows overcoming the limitations of prevailing techniques against the S2- interference. In addition to UV titration for the determination of CN-, we also added fluorescence titration experiments. CN- of 0.1 ?M can also be detected by fluorescence titration. Moreover, the probe was successfully used to detect amygdalin content in almonds. Compared with high-performance liquid chromatography (HPLC), this method avoids the complexity of the extraction process and the interference of polar components. Furthermore, the results are consistent with those obtained by the HPLC method.

Automated summary

The TEO probe showed high selectivity and sensitivity to CN-, overcoming interference effectively. Both UV and fluorescence titration methods can detect CN- as low as 0.1μM. Moreover, the method was successfully applied to detect amygdalin content in almonds.