Gas Chromatography - Mass Spectrometer (GC-MS)

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Gas chromatography - Mass Spectrometry is a common combination for specific detection and identification of chemical substances. The gas chromatography (GC) technique is used for initial separation of the sample components which then are introduced into the mass spectrometer (MS) to be sorted according to their mass-to-charge ratios. Initially, the sample is vaporized (the gas phase) and separates its various components using a capillary column packed with a stationary (solid) phase. As the components become separated, they elute from the column at different times, which is generally referred to as their retention times.Once the components leave the GC column, they are ionized by the mass spectrometer using electron or chemical ionization sources. Ionized molecules are then accelerated through the instrument’s mass analyzer, which quite often is a quadrupole or ion trap. It is here that ions are separated based on their different mass-to-charge (m/z) ratios.The final steps of the process involve ion detection and analysis, with compound peaks appearing as a function of their m/zratios. Peak heights, meanwhile, are proportional to the quantity of the corresponding compound. A complex sample will produce several different peaks, and the final readout will be a mass spectrum. Using computer libraries of mass spectra for different compounds, the unknown compounds and analytes can be identified. 

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