Ultraviolet (UV) Spectroscopy – The Output
The output from a UV scanning spectrometer is not the most informative looking piece of data!! It looks like a series of broad humps of varying height.
Absorbance has no units – it is actually the logarithm of the ratio of light intensity incident on the sample divided by the light intensity leaving the sample.
There are two particular strengths of UV
(i) it is very sensitive
(ii) it is very useful in determining the quantity of a known compound in a solution of unknown concentration. It is not so useful in determining structure although it has been used in this way in the past.
The concentration of a sample is related to the absorbance according to the Beer Lambert Law.
Beer Lambert Law A = e.c.l
A = absorbance
c = concentration in moles l-1
l = pathlength in
e = molar absorptivity (also known as extinction coefficient) which has units of moles-1 L cm -1.
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