6.10.4

Gas Chromatography (A2 Only)

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Gas Chromatography

Gas chromatography (GC) is another type of chromatography.

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Experimental setup

  • A column is packed with a solid.
  • A mixture of the vaporised sample is passed through the column in an inert carrier gas under pressure at high temperature.
  • The sample needs to be a gas, liquid or volatile solid to be carried through the column.
  • The high temperature causes the sample to vaporise.
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Mobile and stationary phases

  • The mobile phase is the inert carrier gas.
  • The stationary phase is the solid in the column.
  • The most volatile substances will elute from the column first as they will spend more time in the mobile phase.

GC-MS

GC-MS is gas chromatography coupled with mass spectrometry.

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Use of a mass spectrometer

  • Mass spectrometry identifies the components of a mixture from their m/z values.
  • It can analyse the substances in a mixture, but they must be separated first.
    • So the GC can separate the substances in the mixture.
    • The MS can then identify each substance eluted.
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Adding a mass spectrometer

  • Mass spectrometry can be used alongside gas chromatography to increase the analysis of a substance.
    • It is simply done by attaching a mass spectrometer to the GC apparatus.
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The two work well together

  • Gas chromatography is good at separating substances in a mixture but bad at identification.
  • Mass spectrometry cannot separate substances but is very good at identifying them.
    • The two can be used together to play to both of their strengths.
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The process in GC-MS

  • A mixture is added to the gas chromatographer as usual.
  • Each substance eluted from the GC is then directly analysed by a mass spectrometer using their m/z values.

Jump to other topics

1Physical Chemistry

2Physical Chemistry 2 (A2 Only)

3Inorganic Chemistry

4Inorganic Chemistry 2 (A2 Only)

5Organic Chemistry 1

6Organic Chemistry 2 (A2 Only)

6.1Optical Isomerism (A2 Only)

6.2Aldehydes & Ketones (A2 Only)

6.3Carboxylic Acids & Esters (A2 Only)

6.4Aromatic Chemistry (A2 Only)

6.5Amines (A2 Only)

6.6Polymers (A2 Only)

6.7Biological Organic (A2 Only)

6.8Organic Synthesis (A2 Only)

6.9NMR Spectroscopy (A2 Only)

6.10Chromatography (A2 Only)

6.11A-A* (AO3/4) - Organic 2

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