Gas Chromatography - Mass Spectrometry is a common combination for specific detection and identification of chemical substances. The gas chromatography technique is used for initial separation of the sample components which then are introduced into the mass spectrometer to be sorted according to their mass-to-charge ratios. GC-MS analysis is commonly used in the pharmaceutical and food industries, but also used in detection of unknown samples, eg environmental analysis, forensic science, fire detection and explosives investigations.