Flame Ionization Detector

Flame ionization detector (FID):

Hi friends, today we will learn flame ionization detector and its working.

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The diagram shows the flame ionization detector used in gas chromatography. It consists of a burner in which the effluent in the burner is mixed with hydrogen and air. This mixture is then ignited electrically. Most of the organic compounds when paralyzed at the temperature of H2/air flame, they produce ions and electrons which can conduct electrically through flame. A potential of few hundreds volts is applied across a burner tip and collector electrode located above the flame. The resulting current is then directed into a high impedance operational amplifier circuit for the measurement. Now as the number of ions produced in the flame is near about proportional to the number of carbon atoms, the current produced is also proportional to the carbon atoms in the sample.

Flame Ionization Detector
Flame Ionization Detector

The flame ionization detector is powerful detector for the analysis of organic samples because of insensitivity of flame ionization detector towards the functional groups like carbonyl, alcohol, halogen and amine as well as the noncombustible gases like H2O, CO2, NOx. It is particularly used for the detection of pollutants in natural water sample.

Advantages of flame ionization detector:

  • 1)      High sensitivity (10^-13 gm/sec.)
  • 2)      Large linear response range (10^7)
  • 3)      Low noise
  • 4)      Rugged and easy to use

Limitations of flame ionization detector:

1)      Destructive to the sample.

You may also like:

• Thermal conductivity detectors
• Liquid Chromatograph (HPLC)
• Argon ionization detector
• Electron capture detector

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