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 ofwith, but the mixture ofwithshowed 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 withrationalized as a complex formation with 1:1 stoichiometry, with an average value for the association constant () of (12 ± 1) x 10M, and a quantum yield ratio between the complexedand 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 forin 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.