Importance of Gas Liquid Chromatography

Gas Liquid chromatography (GLC) is an important technique for analytical chemists as compounds can be separated and analysed by vaporisation without decomposition. 

Although it is similar to other column chromatography techniques, there are also differences. 

from Chemtech :

Firstly, the process of separating the compounds in a mixture is carried out between a liquid stationary phase and a gas moving phase, whereas in column chromatography the stationary phase is a solid and the moving phase is a liquid. (Hence the full name of the procedure is Gas-liquid chromatography, referring to the mobile and stationary phases, respectively.) Secondly, the column through which the gas phase passes is located in an oven where the temperature of the gas can be controlled, whereas column chromatography (typically) has no such temperature control. Thirdly, the concentration of a compound in the gas phase is solely a function of the vapour pressure of the gas.

It is a simple, sensitive and effective in separating components in a mixture and in quantifying the amount of components present.  Both qualitative and quantitative analyses are both possible with GLC. 

Qualitative

We can identify unknown components in a mixture by comparing retention times with known standards. However, this is only tentative. If we stronger matching, we combine GC with mass spectrophotometry and use mass spec to identify the components. 

Quantitative

We can find the concentration of the component by using the peak areas, which is proportional to the concentration. It can be calculated by using a calibration curve, derived from a series of analytes

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Application of GC 

Food analysis

from ars.usda.gov:

Gas chromatography (GC) is used widely in applications involving food analysis. Typical applications pertain to the quantitative and/or qualitative analysis of food composition, natural products, food additives, flavor and aroma components, a variety of transformation products, and contaminants such as pesticides, fumigants, environmental pollutants, natural toxins, veterinary drugs, and packaging materials.

Forensics

 from justchromatography:

GC is widely used by forensic scientists – from analysis of body fluids for the presence of illegal substances, to testing of fiber and blood from a crime scene, and to detect residue from explosives.

They have also found the use of GC with differential mobility spectrometry as a cheap, on location method of detection for flammable liquids used in crimes of arson. 

In conclusion, Gas chromatography is useful in helping us understand and identify unknown components, whether it is in student labs, food analysis and even in solving crimes.