Gas Chromatography

Louvain-La-Neuve

Gas Chromatography is a technique for separating a mixture of thermostable and volatile molecules.

This method is often used to check the purity of a given substance, or to separate the components of a mixture to determine the relative amounts of each compound.

After volatilization, the compounds are separated thanks to their difference in affinity between the stationary phase of the column and the mobile phase (carrier gas). Compounds with a lower affinity for the stationary phase are eluted from the column faster than compounds with a high affinity. The gas phase, for its part, transports the sample through the column which is coated with a specific material on its internal surface. In general, the diameter of the GC columns is smaller and these are longer than the HPLC columns. The choice of carrier gas depends on the type of detector used, we most often use nitrogen but helium will be the optimum for a mass spectrometer.

The equipment itself is called a chromatograph and has several elements. We have the injector (split/splitless type, generally used) which allows to introduce the sample in whole or in part, a capillary column (polar or apolar), an oven which allows a gradual rise in temperature or to work in isothermal and a detector.

Various detectors are used on the platform.

 

Applications of this technique:

  • Determination of volatile fatty acids (from C2 to C6)
  • Determination of fatty acids, in the form of methyl ester
  • Determination of sugars, in the form of TMS
  • Determination of PAHs and PCBs