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Topic: Absorbance & logarithm epsilon  (Read 8313 times)

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Offline Bidagdha_TADIR

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Absorbance & logarithm epsilon
« on: July 20, 2014, 08:26:45 PM »
Suppose I dissolve a small particle of PABA in methanol and run the solution produced in UV-Visible spectrophotometer at 200-400nm. I will get a absorbance vs. wavelength spectrum. There is no way I can construct a logarithm epsilon vs. wavelength spectrum in this situation.

On the other hand, if I run a solution of 10-6M PABA solution, I will still get a absorbance vs. wavelength spectrum but I can construct a logarithm epsilon vs. wavelength spectrum by changing the absorbance scale to log(absorbance/10-6) scale.

Did I got this, or have I made a mistake?

Offline Corribus

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Re: Absorbance & logarithm epsilon
« Reply #1 on: July 20, 2014, 09:32:37 PM »
You can only calculate the extinction coefficient if you know the concentration, so you are correct. However it's not really appropriate to do this with only a single concentration value. You need at least three, to make sure you are in the linear range.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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