Gas chromatography

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Contents

Definition

An analytical technique used for identification and quantitation of organic volatile compounds and inorganic gases.

Applications

Gas chromatography (GC) is a basic analytical tool, extremely versatile and widely employed for multiple applications in almost every industrial and economic sector; many examples can be found in areas such as environmental, agriculture, food and beverage, energy, petroleum, electronics, forensics, medical services, pharmaceuticals, chemical industry, polymer industry, metallurgy, other research, textiles, explosives, etc.

Method

A sample in the gas phase is injected into an analytical column coated with a stationary phase. The different individual adsorption interactions of the components in the sample with the stationary phase are used to separate each of these components as they are pushed along the column by an inert carrier gas. At the column’s exit, a detection–amplification system linked to a computer and data handling system allows for the detection, quantitation and identification of the separated compounds.

Instrument

The gas chromatography instrument is composed of four fundamental parts:

  • An injection block set at approximately 300ºC capable of quickly heating the sample without decomposing it and delivering it with minimum diffusion to the column’s entrance.
  • A precise temperature controlled oven containing the analytical capillary column (packed columns with an inert solid support coated with the stationary phase are still used for some applications). Chromatographic performance and separation are critically dependent on temperature, therefore temperature control is absolutely necessary for consistent and reproducible results.
  • Detection system. Many different detectors are available, from nearly universal such as mass spectrometric of flame ionisation FID, to very specific detectors such as the NPD for the detection of nitrogen and phosphorous containing compounds or the atomic emission detector (AED) for metal detection and identification. Highly sensitive detectors such as mass spectrometric MS or electron capture ECD are available for different applications, each with unique properties and advantages.
  • Computer system and data handling software.
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