Because of its relatively high sensitivity to most organic compounds, the flame ionization detector is a powerful tool for measuring hydrocarbon impurities in other gases. It also provides a linear response over a wide range of analysis.
The figure shows the general construction of an FID. Organic compounds from the sample stream or separation column are injected into the detector housing where they are mixed with Hydrogen and air before entering the detector jet where the mixture is burned.
During this process, organic compounds are broken down into carbon fragments and acquire a positive charge (i.e., become ionized) at the surface of the anode. Carbon fragments are detected by the collector. The signal is then amplified and sent to the data processing system.
