Gas chromatography

Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. This technique is typically used for testing the purity of a particular substance, or separating the different components of a mixture. In some situations, GC may help in identifying a compound.

Principle

Gas chromatography is in principle similar to column chromatography, but has several notable differences. The sample solution injected into the instrument enters a gas stream which transports the sample into a separation tube known as the "column." Helium or nitrogen is used as the carrier gas to transport the molecules through the column.

Components

A gas chromatograph is a chemical analysis instrument for separating chemicals in a complex sample. A gas chromatograph uses a flow-through narrow tube known as the column, through which different chemical constituents of a sample pass in a gas stream (carrier gas) at different rates depending on their various chemical and physical properties and their interaction with a specific column filling, called the stationary phase.

Injector

The injector serves to introduce the sample into the continuous flow of carrier gas. The injector should introduce the sample in a reproducible manner and without causing sample decomposition.

Column

The column is where the components are separated; it is the heart of the system. The column can be packed or capillary. Packed columns are the routine and economical option, and are still widely used for routine analyses.

Detector

The detector is the device that sees the separated components; it provides a signal proportional to the amount of sample component emerging from the column. Hence, the detector is the sensing portion of the system.

Applications

Gas chromatography is widely used in applications involving pharmaceuticals, food chemistry, fire investigation, environmental analysis, and explosives investigation. It is also used in the advancement of medicine, science, and technology.

See also

• Liquid chromatography
• High-performance liquid chromatography
• Thin layer chromatography

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