13-HYDROXYACENAPHTO[1,2-B]QUINOLIZINIUM BROMIDE AS A NEW FLUORESCENCEINDICATOR

13-Hydroxyacenaphtho[1,2-b]quinolizinium bromide (13-HQBr) was selecte d as a fluorescence indicator to determine basic compounds in non-aque ous media. This compound possesses an acidic phenolic hydroxyl group. It presents varying absorption (R-OH, 408, 430 nm; R-O- 456, 478 nm) a nd excitation spectra (R-OH, 425 nm; R-O-, 471 nm) depending on the pH of the media, but the same emission fluorescence spectrum (R-OH = R-O -, 526 nm) at different pH in buffered aqueous solutions. However, in acidic non-aqueous media (acetic, formic and trifluoroacetic acids), i t can be observed that the fluorescence emission spectra differ for th e ionized (lambda(em) = 530 nm) and non-ionized (lambda(em) = 440, 470 nm) forms. The fluorescence intensity at the characteristic peaks dep ends on the acid-base equilibria in the ground and excited states. The refore, this property could be used to evaluate the concentration of b asic compounds, showing a good linearity range between fluorescence in tensity and basic sample concentration.