Comparing High Pressure Liquid Chromatography and Gas Chromatography

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Comparing High Pressure Liquid Chromatography and Gas Chromatography

HPLC and GC have different approaches to separating components in mixtures. HPLC deals with separating particularly non-volatile and liquid substances such as ions, polymers and other complex structured molecules into their components; whereas, GC deals with volatile and gaseous substances or the substances could be vaporised (organic or inorganic molecules such as alcohols) while they are in the injection unit.

In HPLC high pressures are given from a pump in order to force the mobile phase through the column and interact with the components within the mixture. This is because compounds that react very slowly due to their complex structure are being separated within the column. A vacuum degasser is also present in HPLC and it removes the air bubbles that are in the mobile phase; otherwise these air bubbles will give false peaks in the chromatogram.

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On the other hand, Gas Chromatography, highly volatile substances such as alcohols are being separated in a mixture, therefore a very high pressure is not necessary because in GC the components are volatile and they do not have to be forced to interact with the mobile phase and the stationary phase because the components themselves are reactive; instead components travel through the stationary phase with capillary action. Heat is being used instead in GC to turn the mixture into gas form in order for the gaseous mobile phase to carry it along the column; the temperature can be controlled by ...

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