| Abstract: | The Stern-Volmer constant for the quenching of quinine fluorescence by chloride ions has been found to be markedly dependent on acid concentration. Steady-state and time-resolved fluorescence measurements under different acid and salt concentrations have further shown that the decrease in quenching arises from the influence of increasing ionic strength on the diffusion-controlled rate constant for the bimolecular quenching process. Two possible mechanisms for this dependence are discussed: a decrease in the intrinsic rate constant for the reaction due to the kinetic salt effect, and a decrease in the effective encounter distance due to screening of the charges on the reactants. © 1996 John Wiley & Sons, Inc. |
