Gas chromatography (GC) and mass spectrometry (MS) is used to separate and analyze compounds from a complex mixture that can be readily vaporized (typically non-polar compounds below 500 Da). The GC vaporizes the sample, then separates and analyzes the various components. Each component produces a specific retention time and EI mass spectrum of the eluting components. The size of the peaks is proportional to the quantity of the molecule. The compound can be identified by the GC retention time, the parent ion, and fragmentation pattern as searched by a database of known compounds. The retention time can help to differentiate between some compounds.