GC-MS is a chemical analysis technique widely used to identify chemical components, contaminants, and trace elements within a specimen. It combines two powerful techniques to separate and analyze constituents of, typically, volatile compounds. In the Gas Chromatography (GC) process, the sample is vaporized and carried over a packed capillary column, where they are separated. Sample constituents are identified by comparing them against reference standards. The components leaving GC are ionized and fragmented as they enter the Mass Spectrometer. A mass analyzer (e.g., a quadrupole detector) separates and analyzes the ionized molecules based on their mass to charge ratio (m/z). Peaks appear as a function of m/z, and these reproducible mass spectra are used to identify the molecules and perform quantitative analysis.

Running GC tandem with multiple, variant MS detector units adds additional fragmentation steps for the sample components. Tandem MS is beneficial for identifying and analyzing targeted molecules, where low detection limits are required. Examples of such variants include GC-MS/MS or GC/MS-TOF (Time of Flight). Options like Selected Ion Monitoring (SIM) in MS are also available for quantitative analysis of trace components.