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Homework Help: Liquid seperation of B-carotene and Chlorophyll-a

  1. Nov 10, 2006 #1
    Hi all, I have just done a liquid seperation of B-carotene and Chlorophyll-a and put the 2 samples through a UV spectrometer.

    The result that I get from the meter for B-carotene is 448nm for 1st peak and 475.1nm for 2nd peak.

    For Chlorophyll-a my peaks are at 417.9nm and 666.1nm.

    But I have a few questions here. Why are there 2 peaks for each of them? Is it normal? Is it due to the presence of impurities? Is it due to me not choosing the appropriate blank for the UV spectrometery test?

    For the case of B-carotene, the 2 peaks are so close together which means they have really poor resolution. Is it normal?

    Thanks in advance for anyone who can offer me a little guidance.


  2. jcsd
  3. Nov 11, 2006 #2


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    B-Carotene and Chlorophyll-a are conjugated organic molecules, the excitation spacing (pi to pi) for B-Carotene is closer together in the visible region since it's more conjugated. A lot of this stuff can be explained quantitatively by the particle in a box model.

    You can ascertain the color of the solution by employing color methods, the two peaks represent the wavelengths that the molecule absorbs, familiarize yourself with some of the basic principles of "color theory" to understand why B-Carotene appears orange, for instance.
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