Calixarenes and cyclodextrins as off- and on-fluorescence probes for carbazole

Absorption and fluorescence spectra of the nitrogen polycyclic aromatic hydrocarbon carbazole ( ) were analyzed with native cyclodextrins ( ; , , ); derivatized (hydroxypropyl- -cyclodextrin, ; methyl- -cyclodextrin, ) and p-sulfonated calixarenes ( , with n = 6 and 8) macrocycles. The results showed a slight increase in the absorbance of with , but the mixture of with showed lower absorption than the sum of the individual spectra. Also, changes in fluorescence were observed by adding the macrocycles, quenching with , and significant increases with . The higher fluorescence enhancement was with rationalized as a complex formation with 1:1 stoichiometry, with an average value for the association constant ( ) of (12 ± 1) x 10 M , and a quantum yield ratio between the complexed and free (Φ /Φ ) of (1.56 ± 0.02) at neutral pH and 25.0 °C. These increases in fluorescence were used as an on-fluorescence switch to develop a supramolecular analytical method for in aqueous samples. The best analytical parameters were in (LOD = 1.41 ± 0.01 ng mL ). The method was validated in aqueous samples of river and tap water with recoveries between 96%-104%. The proposed supramolecular method is quick, direct, selective and represents an alternative and low-cost analysis method.