Partly quenched, synchronously excited fluorescence emission spectra in the characterisation of complex mixtures

Abstract

Non-linear quenching of mixed fluorescences at low concentrations of quencher, and linear variation at increased concentrations, depend on the Stern-Volmer coefficients and on the proportions of the components in a manner that can be predicted from the Stern-Volmer equation. The variation with quencher concentration of emission intensities synchronously excited from mixtures of benzo[a]pyrene and perylene at intervals of 45 nm is quantitatively interpreted in this way.

A variety of examples is used to show that in the qualitative characterisation of complex mixtures the specificity of synchronously excited spectra is enhanced by the use of varyingly quenched conditions. The high resolution afforded by the synchronous excitation technique readily demonstrates the widely differing relative sensitivities of components of fluorescent mixtures to quenching effects; and reveals new emissions that are obscured under non-quenching conditions.