Process gas chromatography is one of the most powerful measuring and analysis methods for process engineering. It is a procedure which is both discrete and extractive. This method is frequently used for online operation monitoring because the processes can be easily automated and a large number of components can be measured simultaneously.

Process gas chromatography can be used to separate and quantify the components of almost all homogenous gaseous or liquid mixtures. It must be possible to vaporize the liquid components without decomposition. The individual components of a discrete sample pass through the column system at different velocities, and are recorded in succession by a detector.

The time between sample introduction and registering of a substance at the detector (retention time) is characteristic of the substance and can also be used for the identification. The magnitude of the detector signal is a measure of the volume concentration of the component in the gas or liquid.