Chromatography

F324

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  • Created by: Kath
  • Created on: 01-06-14 13:24

1. Why is it important to seal the jar containing the TLC plate?

  • to allow the process to occur
  • to slow the evaporation of the solvent from the TLC plate
  • to speed up evaporation of the solvent
  • to prevent bacteria contaminating the sample
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2. Which is NOT a limitation of thin layer chromatography?

  • may be difficult to find a solvent which will separate all components
  • similar compounds have similar Rf values
  • similar compounds have similar retention times
  • unknown compounds have no Rf value for comparison

3. What does a liquid stationary phase separate by?

  • relative solubility
  • adsorption
  • absorption

4. What is the benefit of coupling gas chromatography with mass spectrometry

  • gas chromatography separates compounds and mass spectra can be compared to a database
  • both the retention time and mass spectra can be used to improve the reliability of the identification
  • mass spectroscopy separates the compounds and retention times can be compared to a database

5. Which is NOT a limitation of gas chromatography?

  • unknown compounds have no reference Rf value
  • substances have the same retention times
  • unknown compounds have no reference retention time
  • substances can 'hide' beneath each other so will not be detected

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