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Comparing High Pressure Liquid Chromatography and Gas Chromatography

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Introduction

´╗┐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. ...read more.

Middle

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 a thermostatically controlled oven; the HPLC is done at room temperature conditions. Also in GC the mobile phase is a gas such as nitrogen or helium; in HPLC, the mobile phase is in a liquid state and is usually polar such as the mixture of water and methanol. UV light is absorbed by components after they are separated from the mixture in HPLC and the amount of light they absorb is detected by sensors in the UV Light Spectrometer. ...read more.

Conclusion

It helps to identify them. Some other common HPLC detectors are conductivity detectors, fluorescence detector and evaporative light detectors. A special detector used in GC is the flame ionization detector. This detector senses the individual components in the mixture as it uses hydrogen gas that burns in air. In GC, the separation of the components in the mixture typically depends on how volatile they are, the most volatile component leaves the column first. Whereas, in HPLC polarity affects the separation of the components; usually non-polar stationary phases are used, and more polar mobile phases carry the more polar component out of the column and into the detector at a faster rate. The non-polar components will take more time to exit the column as they will spend more time attached to the non-polar stationary phase. ...read more.

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