After the components of a mixture are separated using gas chromatography, they must be detected as they exit the GC column. The links listed below provide the details of some specific GC detectors. The thermal-conductivity (TCD) and flame-ionization (FID) detectors are the two most common detectors on commercial gas chromatographs. The requirements of a GC detector depends on the separation application. For example, one analysis might require a detector that is selective for chlorine-containing molecules, another analysis might require a detector that is non-destructive so that the analyte can be recovered for further spectroscopic analysis.
The ECD is as sensitive as the FID but has a limited dynamic range and finds its greatest application in analysis organic molecules that contain electronegative functional groups, such as halogens, phosphorous, and nitro groups.