A fluorescence quenching-based sensor using new metallo-tetraazaporphyrin dye as a recognition element for aniline assay in aqueous solutions

Determination of aniline using metallo-tetraazaporphyrin dyes in CH2Cl2 solutions is described. Seven newly synthesized dyes were screened for the purpose. It was found that fluorescence emission between 700 and 800 nm of the new metal complex dye, octakis(methylthio)tetraazaporphyrinzinc(II) at λmax 505 nm excitation was effectively quenched by the presence of aniline at submicromolar concentrations. The magnitude of quenching depended linearly upon the concentration of aniline in the investigated concentration range of 5.32 × 10−7 to 2.66 × 10−6 M. Therefore it was used in the determination of aniline in the CH2Cl2 extracts from the spiked aqueous solutions. Interference by the other metal ions at 10 and 100 fold higher concentrations in the aqueous solutions was also investigated. The reported method is highly sensitive and showed very low detection limit of 9.87 × 10−8 M in CH2Cl2 solution that corresponded to 1.06 × 10−7 M aniline in water samples containing micromolar amounts of interfering metal ions. Despite of the simplicity of the method it gave highly reproducible results.