What is Gas chromatography?
'''Gas chromatography''' is a type of [[chromatography]]. The sample that is going to be tested is first turned into a gas, and then carried through a column by a nonreactive 'carrier' gas such as [[helium]] or other inert gas such as nitrogen. As the sample is carried through the column it is separated into its individual components. To achieve this the column is housed inside an oven, where the temperature is controlled to allow the individual components to exit the column at different times. == Instrument == === Carrier gas === In selecting a carrier gas it is important to select a gas that will not react with the components of the sample. The carrier gas should also be able to withstand high temperatures due to the oven. The flow rate of the carrier gas is important in that if it is too high there is not enough time for the sample to interact with the column and no separation will be seen, if it is too slow the experiment may take a very long time. === Column === The main type of columns used in gas chromatography is a capillary column. Packed columns are created of fused silica or stainless steel. To increase separation of a gas sample columns must be created of a large length and are coiled to fit inside of the oven. Capillary columns are separated into two categories; wall coated open tubular and support coated open tubular. WCOT are capillary tubes with a thin layer of stationary phase, and in SCOT, the tube is lined with a thin film of support material. As the sample moves through the column the individual parts of the sample become contained with the material inside of the column and are then released. This action allows for a sample to become separated. === Oven === It is important that the oven is capable of maintaining a constant temperature. Since movement of the sample through the column relies on the boiling point of the sample being analyzed, the oven should be set to a temperature that is slightly higher than its boiling point. For samples with a large boiling range, a temperatur