The quantum efficiency of fluorescence ff can be written as
where t is the observed lifetime of the excited state in the
presence of a quenching agent and t0 is the natural lifetime in the absence of
a quencher. The fluorescence radiant power F is given by Equation 15-7. This
quantity is affected by collisional quenching because the lifetime t is
influenced by collisional quenching. Derive an equation to show that the F-t
ratio is independent of collisional quenching and directly related to
concentration. (From G. M. Hieftje and G. R. Haugen, Anal. Chim. Acta, 1981,
123, 255, DOI: 10.1016/S0003-2670(01)83178-0.)
The following lifetimes were measured for the chloride
quenching of quinine sulfate given in Example 15-1. The fluorescence
intensities are given in the example.
(a) Plot fluorescence intensity versus [Cl–].
(b) Plot the ratio of intensity to lifetime, F-t versus [Cl–].
(c) Develop a normalization factor to correct the measured
fluorescence intensity to that of the solution without quencher.
(d) Plot on the same graph F versus [Cl–] and Fcorr