Room-temperature phosphorescence of 6-bromo-2-naphthol included in beta-cyclodextrin in the presence of cyclohexane

The formation constant for a 1:1 binary complex between 6-bromo-2-naphthol (6B2N) and beta -cyclodextrin (CD) in aqueous solution was determined by bo th absorptimetric and fluorimetric methods. Room-temperature phosphorescenc e (RTP) was induced by adding small amounts of different apolar liquids as the third component, with cyclohexane producing the strongest enhancement e ffect. Microcrystals formed in the ternary system seem to be necessary for obtaining phosphorescence emission. The deoxygenation by flowing nitrogen d oes not improve the RTP signals, while the addition of sodium sulfite as ch emical deoxygenant produces quenching of the signals. The calibration graph for 6-bromo-2-naphthol in the presence of beta -CD and cyclohexane was lin ear for the range of concentrations between 0.04 and 1 mug ml(-1), with a d etection limit of 0.04 mug ml(-1). (C) 2001 Elsevier Science B.V. All right s reserved.