How Work Flame Ionization Detection (FID) in TVA-1000B?

Flame Ionization Detection (FID)

A Flame Ionization Detector (FID) measures organic compounds by utilizing a flame produced by the combustion of hydrogen and air. When hydrocarbons in the sample are introduced to the detection zone, ions are produced by the following reaction:

RH + O → RHO+ + e– → H2O + CO2

where
R = carbon compound
A collector electrode with a polarizing voltage is also located within the detector chamber, and the ions produced by this reaction are attracted to it. As the ions migrate towards the collector,a current is produced which is directly proportional to the concentration of hydrocarbons introduced to the flame. This current is then amplified and sent to a microprocessor and/or analog readout device.
The FID has a wide dynamic range. The effective dynamic range can be further expanded by use of a dilutor kit which reduces very high volatile organic compounds (VOC) concentrations to within the dynamic range (or even linear range) of the analyzer. The dilutor kit can also be used to enrich oxygen deficient samples by adding ambient air that is rich in oxygen (20.9% usually). Low oxygen can affect the characteristics of the hydrogen flame, causing readings to be artificially elevated and possibly extinguishing the flame. As a general rule of thumb, greater than 16% oxygen is required to support the flame. If underground gases or samples in gas bags are to be measured by an FID, it is advised that the dilutor be used to combat the problem.

Benefits of Flame Ionization Detection

♦ Wide dynamic and linear range
♦ High sensitivity to hydrocarbon vapors (including methane)
♦ Very stable and repeatable response
♦ Virtually unaffected by ambient levels of CO, CO2, and water vapor