GC/FID

In GC/FID, the FID or flame ionization detector detects analytes by measuring an electrical current generated by electrons from burning carbon particles in the sample.

The flame ionization detector (FID) is a non-selective detector used in conjunction with gas chromatography. Because it is non-selective, there is a potential for many non-target compounds present in samples to interfere with this analysis and for poor resolution especially in complex samples. The FID works by directing the gas phase output from the column into a hydrogen flame. A voltage of 100-200V is applied between the flame and an electrode located away from the flame. The increased current due to electrons emitted by burning carbon particles is then measured. Although the signal current is very small (the ionization efficiency is only 0.0015%) the noise level is also very small (<10-13 amp) and with a well-optimized system, sensitivities of 5 x 10-12 g/ml for n-heptane at a signal/noise ratio of 2 can be easily realized. Except for a very few organic compounds (e.g. carbon monoxide, etc.) the FID detects all carbon containing compounds. The detector also has an extremely wide linear dynamic range that extends over, at least five orders of magnitude with a response index between 0.98-1.02.