title: 13-Hydroxyacenaphato[1,2-b]quinolizinium bromide as a new flouorescence indicator.
abstract: 13-Hydroxyacenaphtho[1,2-b]quinolizinium bromide (13-HQBr)was selected as a fluorescence indicator to determine basic compounds in non-aqueous media. This compound possesses an acidic phenolic hydroxyl group. It presents varying absorption (ROH, 408, 430 nm; RO(-) 456, 478 nm) and excitation spectra (ROH, 425 nm; RO, 471 nm) depending on the pH of the media, but the same emission fluorescence spectrum (ROH = RO(-), 526 nm) at different pH in buffered aqueous solutions. However, in acidic non-aqueous media (acetic, formic and trifluoroacetic acids), it can be observed that the fluorescence emission spectra differ for the ionized (lambda(em) = 530 nm) and non-ionized (lambda(em) = 440, 470 nm) forms. The fluorescence intensity at the characteristic peaks depends on the acid-base equilibria in the ground and excited states. Therefore, this property could be used to evaluate the concentration of basic compounds, showing a good linearity range between fluorescence intensity and basic sample concentration.
authors.affiliation: Laboratorio de Técnicas Instrumentales, Facultad de Farmacia, Universidad Complutense de Madrid, 28040-Madrid, Spain.
authors.forename: M A
authors.initials: MA
authors.lastname: Martin
authors.forename: B
authors.initials: B
authors.lastname: Del Castillo
authors.forename: P
authors.initials: P
authors.lastname: Prados