How does a Flame Ionization Detector (FID) create ions for measurement?

A Flame Ionization Detector (FID) operates by utilizing a hydrogen flame to create ions for measurement. In this process, a sample is introduced into the flame, where it undergoes combustion. During combustion, organic compounds present in the sample are oxidized, leading to the production of positively charged ions and negatively charged electrons.

The hydrogen flame provides the necessary energy for this ionization process, enhancing the detection of the resulting ions. The FID measures the current produced by these ions as they pass between two electrodes. The current is proportional to the concentration of organic compounds in the sample, which allows for quantification.

This method is particularly effective for detecting volatile organic compounds because the flame ionization is sensitive to the presence of hydrocarbons. Other methods of ionization, such as those involving heated coils, UV radiation, or electrical currents, do not operate in the same manner as an FID and are associated with different detection principles.