SHAPE OF ACID-BASE FLUORESCENCE EMISSION TITRATION CURVES IN THE PRESENCE OF BUFFER AND QUENCHING EFFECTS

New theoretical expressions to account for adiabatic and diabatic exci ted-state proton transfer in water, as well as the effect of the prese nce of added buffers, have been deduced for steady-state fluorescence emission measurements. These expressions are easy to manipulate and ad equate for the calculation of rate constants by fitting of experimenta l data. A systematic procedure to obtain kinetic parameters of the sev eral excited-state processes involving proton transfer is also propose d. Finally, the expressions have been tested on the parametrization of the titration curves followed by steady-state fluorescence emission o f phenol, beta-naphthol, alpha-naphthol and acridine. In the particula r case of alpha-naphthol and acridine we were able to describe and cha racterize for the first time, the diabatic quenching effect of a buffe r.