Mass spectrometry is the direct determination of the ratio of mass number to charge (m/z) of a substance, and is both accurate and fast in qualitative analysis. The joint use of chromatography and mass spectrometry is actually the use of the mass spectrometer as a universal detector of the chromatograph.

There are various classifications of GC-MS, for example, according to the analysis scale: small GC-MS and large GC-MS. According to the resolution can be divided into: low resolution gas chromatography mass spectrometry, medium resolution gas chromatography mass spectrometry and high resolution gas chromatography mass spectrometry.

These instruments can realize the separation and identification of target organic compounds in drugs or nutritional products, molecular weight determination and structural analysis of unknown organic compounds, as well as the separation and identification of drugs or their metabolites in samples of body fluids, and many other functions.