A) Calculate the molar absorpt
A) Calculate the molar absorptivity constant at eachconcentration for all wavelengths
B) Determine which wavelength you would use to run a calibrationcurve for the sample and defend the answer
C) Explain why there are differences at each wavelength (ifthere are any) for the calculated molar absorptivity constant
|
Path length for all exps = 2.5 cm |
Concentration |
Abs @ 315 nm |
Abs @ 320 nm |
Abs @ 325 nm |
Abs @ 330 nm |
Abs @ 335 nm |
|
50 mM |
0.08 |
0.12 |
0.23 |
0.20 |
0.18 |
|
|
100 mM |
0.16 |
0.23 |
0.47 |
0.39 |
0.37 |
Answer:
Ans. #A. Beer-Lambert’s Law, A = e C L – equation1
where,
A= Absorbance
e= molar extinction coefficient (M-1cm-1)
p= path length (in cm)
C= concentration
Now,
e = A / C L
The result is tabulated below-
#B. The wavelength giving maximum value ofmolar extinction coefficient (e) is preferred for running thecalibration curve. At this wavelength, the absorbance is maximumand there is minimum changes of error due to interferingcontaminants.
Therefore, wavelength 325 nm is preferred.
#C. As wavelength differ, the energy of photon(E = hv = hc/ l ; where, E = energy, h = Plank’s constant, c =speed of light, l = wavelength). Since absorption of photons isquantized, each molecule absorbs maximum quanta of light atspecified wavelength depending on the nature of the molecule.
So, due to difference in energy content, the molecule absorbslight of different wavelength at different extent leading to thedifference in molar absorptivity constant at differentwavelengths.
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