3.9.3

Gas Chromatography

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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

1.1Atoms, Molecules & Stoichiometry

1.2Atomic Structure

1.3Chemical Bonding

1.4States of Matter

1.5Chemical Energetics

1.6Electrochemistry

1.7Equilibria

1.8Partition Coefficient

1.9Reaction Kinetics

2Inorganic Chemistry

3Organic Chemistry & Analysis

3.1Introduction to Organic Chemistry

3.2Hydrocarbons

3.3Halogen Derivatives

3.4Hydroxy Compounds

3.5Carbonyl Compounds

3.6Carboxylic Acids & Derivatives

3.7Nitrogen Compounds

3.8Polymerisation

3.9Analytical Techniques

3.10Organic Synthesis

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