What is GC-MS?

How the two techniques are coupled

In GC-MS, a vaporised sample is carried by an inert gas through a gas chromatography column, where its components separate by how strongly they interact with the column’s coating, emerging at different retention times. Because the components are already in the gas phase, they pass directly into a mass spectrometer, often after electron ionisation, which breaks each molecule into a reproducible pattern of fragments. The mass spectrometer measures the mass-to-charge ratios of those fragments for each compound as it elutes, giving a mass spectrum tied to each chromatographic peak.

Why combine them

Gas chromatography separates volatile mixtures sharply but identifies peaks only by retention time, which can be ambiguous. Mass spectrometry supplies the missing identity: the fragmentation pattern of each compound is a distinctive fingerprint.

Electron ionisation produces highly reproducible fragment patterns, so they can be matched against extensive reference spectral libraries to name unknown compounds with confidence. This searchable-library identification is a particular strength of GC-MS.

Uses in research

GC-MS is a standard tool for analysing volatile and semi-volatile compounds in forensic, environmental, and food-science research, including drug screening, pollutant detection, and flavour and fragrance analysis. Its complementary partner for larger or heat-sensitive molecules is LC-MS. Reproducible identification depends on standardised methods and on matching spectra to curated, citable reference libraries.