The effect of ionic strength and surfactant on the dynamic quenching of 6-methoxyquinoline by halides

Steady state and time resolved fluorescence measurements have been performed to assess the role of ionic strength and presence of surfactants in the dynamic quenching of 6-methoxyquinoline by halides. The results of quenching by potassium chloride are mainly presented in this paper. The pH dependence of the Stern-Volmer constant has been rationalized in the light of the difference in ionic strengths. The concentration dependent quenching/enhancement of fluorescence by the surfactant, sodium dodecyl sulphate has been observed and explained by considering an equilibrium between free and bound fluorophores and modification of critical micellar concentration of SDS by salts. The concentration of the surfactant has been found to affect the quenching/enhancement of fluorescence by chlorides. Thus, ionic strength and the presence of surfactants are found to be two factors which can affect the sensitivity of the fluorescent probe towards chlorides.