Simultaneous dynamic and static quenching

Static and dynamic quenching may occur simultaneously, resulting in a deviation of the plot of Io/I against [Q] from linearity. 

Let us consider first the case of static quenching by formation of a non-fluorescent complex. The ratio I0/I obtained for dynamic quenching must be multiplied by the fraction of fluorescent molecules (i.e. uncomplexed) 

An upward curvature is thus observed. K v and K can be determined by curve fitting using Eq. (4.29), or alternatively from the plot of (Io/I — 1)/[Q] against [Q], which should be linear. 

Alternatively, using the sphere of effective quenching model, we obtain the following relation instead of Eq. (4.29) 

2 Determination of micellar aggregation numbers by means of fluorescence quenching3  

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