Chromatography

F324

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

1. What is the definition of retention time?

  • the time taken for a particular compound to travel through the column to the detector, from injection to leaving the column
  • the time taken for a particular compound to dissolve in the stationary phase
  • the time taken for the gas to be injected into the column and dissolve in the stationary phase
  • distance moved by component divided by distance moved my solvent front
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2. 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

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

  • to slow the evaporation of the solvent from the TLC plate
  • to allow the process to occur
  • to prevent bacteria contaminating the sample
  • to speed up evaporation of the solvent

4. Which is NOT a use of GC-MS?

  • treatment of strokes
  • airport security
  • forensic analysis
  • drug testing

5. 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

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