Question

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 F_corr versus [Cl^-] .

Short answer

a)

b)

c) Normalization factor = $\frac{{\tau }_0}{\tau }$

d)

Step-by-step solution

Part (a) Step 1: Given Information

Fluorescence intensity versus [Cl^-] should be plotted.

Part (a) Step 2: Explanation

Fluorescence intensity is the dependent variable and the concentration of Cl^- is the independent variable.

Fluorescence intensity	[Cl-], M
180.0	0.000
87.5	0.005
58.0	0.010
43.2	0.015
35.0	0.020
28.5	0.025
24.5	0.030
19.1	0.040
15.7	0.050

Part (b) Step 1: Given Information

The ratio of intensity to lifetime, F-τ versus [Cl^-] should be plotted.

Part (b) Step 2: Explanation

F/τ	[Cl-], M
9.9	0.000
9.8	0.005
10.2	0.010
9.6	0.015
9.7	0.020
10.2	0.025
9.8	0.030
10.1	0.040
9.8	0.050

Part (c) Step 1: Given Information

A normalization factor should be developed to correct the measured fluorescence intensity to that of the solution without quencher.

Part (c) Step 2: Explanation

According to the graph of ratio of fluorescence to the lifetime versus chloride concentration, the ration remains constant even though the concentration of the quencher increases. Therefore$$\begin{gathered} \frac{F_0}{F}=\frac{{\tau }_0}{\tau } \\ {F}_0=F.\frac{{\tau }_0}{\tau } \end{gathered}$$

F₀ – corrected fluorescence (fluorescence without quencher)

F- observed fluorescence (with quencher)

τ₀ –fluorescence life time without the quencher

τ – fluorescence lifetime with the quencher

so the normalization factor is$\frac{{\tau }_0}{\tau }$

Part (d) Step 1: Given Information

F versus [Cl^-] and F_corr versus [Cl^-] should be plotted on the same graph.

Part (d) Step 2: Explanation

F	Fcorr	[Cl-], M
180.0	180.0	0.000
87.5	177.9	0.005
58.0	184.2	0.010
43.2	173.8	0.015
35.0	176.0	0.020
28.5	184.2	0.025
24.5	177.4	0.030
19.1	182.0	0.040
15.7	177.6	0.050