Chromatography is a separation technology. It was invented by Michail T. Swett on 1906. He was Botanist and Physical Chemist. He tried to separate the leaf pigments by passing though the column of CaCO3.
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GC (Gas Chromatography) is using for separation, identification and quantification of volatile organic compounds (boiling point below 350 degree C, though many high boiling compounds can be analyzed by GC after sample pre-treatment) and many inorganic gases.
In case of GC, there is a column which is filled with or coated with some chemicals or materials (and known as stationary phase). An inert gas (we will say mobile phase / carrier gas) pass through this column. Sample introduced in the mobile phase (in gaseous form) which mixes with carrier gas and passes through the stationary phases. During this time, the compounds of interest interacts with stationary phase and one by one comes out from the column and reach to detector. Detector detects the compound as per the working principle of that particular detector. The electronic signal of detector output converts to digital signal and display on output device as a graph.
So, GC has four basic components - Injector, Detector, column oven and integration software.
As the basic has been explained in the document as linked given above, so we will discuss here more about its application.