.The fluorescence of quinine sulfate is quenched by high concentration of chlori
ID: 511366 • Letter: #
Question
.The fluorescence of quinine sulfate is quenched by high concentration of chloride ion. The following fluorescence signals F were obtained as a function of the concentration of chloride ion.
Fluorescence Intensity
[Cl-],M
180
0.00
87.5
0.005
58.0
0.010
43.2
0.015
35.0
0.020
28.5
0.025
14.5
0.030
19.1
0.040
15.7
0.050
Set up a spreadsheet and determine the quenching constant, K.
Fluorescence Intensity
[Cl-],M
180
0.00
87.5
0.005
58.0
0.010
43.2
0.015
35.0
0.020
28.5
0.025
14.5
0.030
19.1
0.040
15.7
0.050
Explanation / Answer
1/F = 1/I ( 1 + KtM)
where F = is the Intensity of fluorescence with a Quencher
I = is the intensity of fluorescence without a Quencher
K = quenching constant
t = Lifetime of emitting species
M = Concentration of the Quencher
1/87.5 = 1/180 ( 1 + Kt. 0.005 )
180/87.5 = (1 + Kt.0.005)
2.057 = (1 + Kt. 0.005)
1.057 = (Kt. 0.005)
211.4 = Kt
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