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Gas chromatography (GC) is an analytical technique used to separate and detect the chemical components of a sample mixture to determine their presence or absence and/or quantities. These chemical components are usually organic molecules or gases.
Gas chromatography (GC) is a common type of chromatography for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture. In preparative chromatography, GC can be used to prepare pure compounds from a mixture.
Gas chromatography is also sometimes known as vapor-phase chromatography (VPC), or gas–liquid partition chromatography (GLPC). These alternative names, as well as their respective abbreviations, are frequently used in scientific literature.
Gas chromatography is the process of separating compounds in a mixture by injecting a gaseous or liquid sample into a mobile phase, typically called the carrier gas, and passing the gas through a stationary phase. The mobile phase is usually an inert gas or an unreactive gas such as helium, argon, nitrogen or hydrogen. The stationary phase can be solid or liquid, although most GC systems today use a polymeric liquid stationary phase. The stationary phase is contained inside of a separation column. Today, most GC columns are fused silica capillaries with an inner diameter of 100-320 μm and a length of 5-60 m. The GC column is located inside an oven where the temperature of the gas can be controlled and the effluent coming off the column is monitored by a suitable detector.
Column technology
GC columns contain a stationary phase, typically a polymeric material. It is through the interaction between the analytes and this stationary phase within the column that separation of the analyte into their molecular components can occur. There are two types of GC columns: packed columns and capillary columns.
Autosamplers
GC, or gas chromatography, autosamplers are instruments that automatically take a sample and insert it into the GC for analysis, which is both more time effective and more reliable than doing it by hand.
Detectors
Detectors used in gas chromatography
Thermal Conductivity Detector.
Flame Ionization Detector (FID)
Thermo Iconic Detector.
Flame Photometric Detector.
Ultraviolet Detectors.
Fluorescence Detector.
Refractive index detector (RI or RID).
Radio Flow Detector.
Mass-spectrometer (MS)
The sample mixture is first separated by the GC before the analyte molecules are eluted into the MS for detection. They are transported by the carrier gas, which continuously flows through the GC and into the MS, where it is evacuated by the vacuum system.
Mass spectrometer (MS) also called GC-MS, highly effective and sensitive, even in a small quantity of sample. This detector can be used to identify the analytes in chromatograms by their mass spectrum. Some GC-MS are connected to an NMR spectrometer which acts as a backup detector. This combination is known as GC-MS-NMR. Some GC-MS-NMR are connected to an infrared spectrophotometer which acts as a backup detector. This combination is known as GC-MS-NMR-IR. It must, however, be stressed this is very rare as most analyses needed can be concluded via purely GC-MS.
