Determination of fluorene in sea-water by room temperature phosphorescence in organised media†

Abstract

Fluorene, insoluble in water, forms an inclusion compound in aqueous media with β-cyclodextrin, with an equilibrium constant of 2290 ± 150 l mol^–1 at 15 °C. The inclusion phenomenon was studied by fluorimetric and phosphorimetric techniques. A schematic host–guest model to explain the inclusion complex structure is reported. The phosphorescence spectra showed maximum excitation and emission wavelengths at 304 and 460 nm, respectively. The phosphorescence lifetimes were calculated employing different organic and inorganic perturber atoms, and was 185 ms for 3-bromopropan-1-ol. Optimum conditions of the method were [β-cyclodextrin] = 8 × 10^–3M, pH = 6.65, 3-bromopropan-1-ol as heavy atom, sodium sulfite–sulfurous acid as oxygen scavenger, β-cyclodextrin, heavy atom and buffer as addition order, temperature 15 °C and t_d and t_g 0.1 and 13 ms, respectively. The main figures of merit were linear dynamic range 15–2000 ng ml^–1, detection limit 4.5 ng ml^–1 and RSD 2.5%. The method has a moderate selectivity against other PAHs and aromatic molecules and a considerable increase in selectivity in comparison with fluorimetric measurements is observed. An application of this technique to fluorene determination in environmental sea-water samples with successful results is described.