Flame ionization detector

A flame ionization detector (FID) is a scientific instrument that measures analytes in a gas stream.

The first flame ionization detectors were developed simultaneously and independently in 1957 by McWilliam and Dewar at Imperial Chemical Industries of Australia and New Zealand (ICIANZ, see Orica history) Central Research Laboratory, Ascot Vale, Melbourne, Australia.

[7] The operation of the FID is based on the detection of ions formed during combustion of organic compounds in a hydrogen flame.

The generation of these ions is proportional to the concentration of organic species in the sample gas stream.

Hydrocarbons generally have response factors that are equal to the number of carbon atoms in their molecule (more carbon atoms produce greater current), while oxygenates and other species that contain heteroatoms tend to have a lower response factor.

The eluent exits the gas chromatography column (A) and enters the FID detector’s oven (B).

This positive bias helps to repel the oxidized carbon ions created by the flame (E) pyrolyzing the eluent.

Flame ionization detectors cannot detect inorganic substances and some highly oxygenated or functionalized species like infrared and laser technology can.

The methanizer is limited by its inability to reduce compounds other than CO and CO2 and its tendency to be poisoned by a number of chemicals commonly found in gas chromatography effluents.

Schematic of a flame ionization detector for gas chromatography.
FID Schematic: [ 11 ] A) Capillary tube; B) Platinum jet; C) Hydrogen; D) Air; E) Flame; F) Ions; G) Collector; H) Coaxial cable to analog-to-digital converter ; J) Gas outlet