Theory of Static Quenching

The dependence of the fluorescence intensity upon quencher concentration for static quenching is easily derived by consideration of the association constant for complex formation. This constant is given by 

We can substitute flucxescence intensities for die fluofo-phc concentrations, and rearrangement of Eq. (8.1 yields 

One additional mediod to distinguish static and ctynamic quenching is by careful examination of die absorption spectra of the fluorophore. Collisional quendiing only affects the excited states of die fluorophores, and dius no changes in the absorption spectra are expected. In contrast, ground-state complex formation will flequently result in perturbation of the absorption spectrum of the fluoioph(xe. In fact, a more complete form of Eq. [8.17] would indude the possibility of different extinction coefficients fbr die free and complexed forms of the fluorophore. 

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