A portion of the sample is placed into a headspace sampling unit at a specified temperature. The gas above the sample is then injected onto a gas chromatography column. Components are separated as a function of temperature and interaction with the column stationary phase. They are then subjected to an electron impact (EI) mass spectrometry source. The resulting characteristic fragmentation patterns are used for component identification. Comparison of the sample spectra to reference spectra for thousands of known compounds often allows for positive component identification. Comparison with a calibration curve for known amounts of the reference material can then be used for quantitation. A three point calibration is standard. This technique only provides information on volatile sample components.