There is a Difference between a Gas detector and a chromatograph.
A "Gas detector" is the principle of gas detection. It can be FID - Flame Ionization Detector or TCD - Thermal conductivity detector.
The chromatograph is a device to identify the gas components in a gas stream. The detection mechanism in a chromatograph can be FID or TCD. The cycle time of a chromatograph determines the types of gases that can be detected.
FID can only measure Hydrocarbons from Methane to Normal Pentane (C1 to C5) whereas TCD can detect both, organic (C1 to C5) as well as Inorganic (CO2)
- FID detectors are more sensitive than TCD
- Values detected by TCD detectors drift over time while FID does not
- Moisture in the gas affects TCD reading but does not affect FID detectors
- FID requires Hydrogen gas while TCD does not require