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

Absorption and fluorescence spectra of the nitrogen polycyclic aromatic hydrocarbon carbazole ( CZL ) were analyzed with native cyclodextrins ( CD ; α , β , γ ); derivatized CD (hydroxypropyl- β -cyclodextrin, HPCD ; methyl- β -cyclodextrin, MeCD ) and p-sulfonated calixarenes ( SCAn , with n = 6 and 8) macrocycles. The results showed a slight increase in the absorbance of CZL with CD , but the mixture of CZL with SCA showed lower absorption than the sum of the individual spectra. Also, changes in fluorescence were observed by adding the macrocycles, quenching with SCA , and significant increases with CD . The higher fluorescence enhancement was with HPCD rationalized as a complex formation with 1:1 stoichiometry, with an average value for the association constant ( K A ) of (12 ± 1) x 10 2 M -1 , and a quantum yield ratio between the complexed CZL and free CZL (Φ CZL-HPCD /Φ CZL ) 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 CZL in aqueous samples. The best analytical parameters were in HPCD (LOD = 1.41 ± 0.01 ng mL -1 ). 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.