Gas Chromatography Detectors: Choosing the Right One

Gas chromatography uses detectors that respond to different kinds of analytes. The main detectors covered here are the thermal conductivity detector (TCD), flame ionization detector (FID), and electron capture detector (ECD). Each one has a different way of turning a separated compound into a signal.

The thermal conductivity detector, or TCD, measures the thermal conductivity of the surrounding gas using thermistors arranged in a Wheatstone bridge circuit.

A Wheatstone bridge involves balancing four resistances in a bridge configuration to determine an unknown resistance by tuning the voltage to zero.

In TCD, pure carrier gas p...