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GAS CHROMATOGRAPHY

 

Trace GC equipped with Flame ionization detector (FID)
Trace GC equipped with Flame ionization detector (FID) and Electron Capture detector (ECD)

Gas chromatography is a separation technique where volatile components of a complex mixture are distributed between a gaseous (mobile) phase and a stationary phase.  A fused silica capillary (10-30 m), internal diameter (0,22 – 0,32 µm) contains a liquid film (0,2 – 5 µm) of a suitable stationary phase (e.g. silicon oil or wax).  Helium is used as the mobile phase which flow continuously through the column.  1 µl of the mixture is injected, a temperature program is started and separation occurs as a function of time due to differences in intrinsic properties of the compounds in the mixture (distribution coefficient, volatility, polarity, Mw) and interaction with the stationary phase.  The separated compounds are detected with suitable universal and selective detectors (e.g. FID, ECD). Flame ionization (FID) is a non-selective detector; electron capture (ECD) is a selective detector for the analysis of halogenated compounds.  In the obtained 2-D plot (the chromatogram) retention time is a qualitative criterium while peak area allows determination of the concentration of the compounds in a mixture after calibration.  A very powerful detector is a mass spectrometer.


Applications

  • Analysis of solvent mixtures in paint and coatings
  • Quality control
  • Analysis of additives
  • Analysis of chlorinated compounds (e.g. PCB’s)