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Writing chemical equations for TLC analysis?

  1. Sep 29, 2011 #1
    I just submitted a lab report for a TLC experiment, but I just realized that I completely forgot to include the "reactions" section. It's too late to save that grade, but for future reference, how would one go about writing out a chemical equation for a TLC experiment? I had always understood solubility to be a purely physical property, meaning that no real reaction would take place. Similarly, polar attractions (or lack thereof) between molecules do not count as reactions either, so what would one put down in such a situation? Anything?

    In this lab, we were given an unknown mixture of two analgesic drugs and asked to identify them based on our TLC testing of four known drugs, aspirin, acetaminophen, caffeine, and phenacetin, using a mixture of hexane, ethyl acetate, and acetic acid as the solvent. We used silica-coated plates.

    Any guidance would be much appreciated.
     
  2. jcsd
  3. Sep 29, 2011 #2

    Borek

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    Staff: Mentor

    TLC is not about any particular chemical reaction.
     
  4. Sep 29, 2011 #3
    That's basically what I thought... Still, do you think it would have been pertinent to the report to write equations that show how the driving process works? That is, for instance, to write out the solvation of phenacetin in the solvent mixture similar to that of NaCl in water
    (NaCl + H2O--> Na+ + Cl- + H2O)?

    Sorry if my question isn't quite clear--I'm having trouble putting it into words. I intend to ask my instructor about it next week, especially if I lose points for not writing out any reactions. I just wanted to try to figure it out now, when it's fresh in my mind (and, unfortunately, when I don't have an opportunity to go see her).

    Thank you for your help.
     
  5. Sep 30, 2011 #4

    Borek

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    Staff: Mentor

    In this particular case I would say forcing yourself to find a reaction equation just to put it in the report doesn't make sense. Reaction should be related to the experiment, not forced into the report.

    It would make much more sense to discuss adsorption equilibrium - in a way that can be described by the reaction equation, even if I would not call adsorption and desorption a "chemical reaction".
     
  6. Oct 1, 2011 #5
    Okay, thank you. I was just a bit nervous about leaving anything out that could potentially be relevant because my instructor is known for being an extremely tough grader. I just wanted to be sure that there wasn't something important that I hadn't thought of. Thanks again!
     
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