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Chromatography Questions

  1. Feb 21, 2004 #1
    I did an experiment in class on Chromatography and extracting pigment material from a leaf and such.

    We took a piece of some special paper put a base line in pencil at the bottom and covered it with leaf extract. Then putting a pin through the top set it in a beaker of acetone and the chemicals rose to the top.

    Anyway how does Chromatography work? Trying to answer some questions but I can't seem to find the type of answer I'm supposed to have.

    I said to the teacher: The surface area in the beaker is lowered when the paper is put inside and forced the materials up. He said I was on the right track with that but it wasn't right.

    Also carotone, chlorophyll A & B, and Xanthrophyl were chemicals apparent at the top of the paper. I took the Rf values and such.

    Anyway I'm suppose to answer what were the roles of carotene and xanthrophyl. I have no clue lol. There is so much stuff of Chromatography on the net its hard to find what I'm looking for. And yes I do pay attention in class. ;)

    Thanks to anyone who can help me out here.
  2. jcsd
  3. Feb 22, 2004 #2


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    Since you're clearly asking about a homework assignment, I'm not going to come straight out and give you the answers, you need to work out some of that for yourself. But here are a few hints. When the acetone moves up the chromatography paper, it's not being "pushed" up from below. Think about the paper itself when trying to explain how the solvent moves up the paper. You'll also need to think about why each pigment stops at a particular place along the paper rather than continuing to move up with the solvent front. Why the solvent keeps moving and the pigment stops are related concepts.

    In terms of the roles of carotene and xanthophyll, your textbook should offer some help. If not, another thing to notice is the color of those two pigments. When and where do you see those colors in plants? That should give you a hint of where to start. The roles of those two pigments is unrelated to chromatography other than that you were able to identify those two separate pigments using chromatography, so when you're looking up information on them, you don't need to look it up in the context of chromatography.
  4. Feb 22, 2004 #3
    Thanks! You helped me be a bit more assured of the hypothesis I had calculated just recently. Sorry if I seemed like I was trying to hide the fact that it was a homework assignment. I was actually just blankly asking because I was stuck. :)

    Anyway after looking up on the net the roles of the two chemicals I'm thinking Combustion is afoot. Regardless as long as I give it an honest effort my teacher will correct me and steer me in the right direction. Thanks for your help. :)
  5. Feb 23, 2004 #4
    The technique you are describing is called Thin Layer Chromatograpy. Most kinds of chromatograpy follow the same general principle, but this should help you look up how this works specifically.

    carotene and xanthophyll have nothing to do with combustion. Consider where you got these from, leaves. (spinach, right?)
  6. Feb 23, 2004 #5
    Thanks for the help. It wasn't combustion but I got the answer changed. I can't recall exactly how it was worded but it was something about capillaries that made it work. The leaf extract's source I'm not certain of.
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