Application Note: Flame Ionization Detector Capabilities

The Flame Ionization Detector (FID) is a widely used detector in gas chromatography. Its linear response to hydrocarbons over many orders of magnitude lends significant analytical capability to numerous routine gas analysis applications. The FID used in AMETEK Process Instruments' Trace Analytical gas purity analyzers is a very sensitive detector. It is used to detect traces of hydrocarbons and CO2 in normal air constituents (O2, N2, etc.) and inert gases.

The hydrocarbons in the sample gas are burned in a hydrogen flame to ionize the carbon atoms which then emit free electrons. These electrons are measured as a current that is in direct proportion to the concentration of the hydrocarbons burned. Normal air constituents, including CO and CO2, do not emit electrons and therefore give no response to the FID. Consequently these gases do not interfere with the measurement. This lack of interference enables the FID to measure hydrocarbons at low ppb levels