Understanding Gas Chromatography in Detail

Understanding Gas Chromatography in Detail Gas Chromatography is a scientific process to discover and distinct the unknown compounds present in a sample mixture. This is widely used to separate organic compounds like RNA and DNA. For separation to be correct in a GC the compound needs to thermally stable and reactive towards temperature. GC works with two different phases of compound i.e. Mobile phase and stationary phase. Gases are used in the mobile phase because their molecules are constantly moving and solid or liquid is used in the stationary phase as their molecules do not move past each other. This process is also known as Vapor Phase Chromatography or Gas-Liquid Partition chromatography.

Working of Gas Chromatography, The two most important factors for GC are difference in temperature or difference in molecule size in a compound. The Gas chromatograph components include a Sample injector, flow controller, GC column, column oven, a detector, and a computer for data calculation. GC setup temperature can vary from 350 to 450 degrees Celsius.

A) Meeting of Inert gases and Sample Compound.

The process begins from a Gas cylinder containing inert gases like Helium and Nitrogen used as the Mobile phase. Inert gases are used as they are non-reactive and do not react with sample compounds. The gas cylinder is joined with a flow controller to control the gas flow towards the Gas chromatograph or the oven.

The sample compound is injected with a sample injector in the inlet. The Inlet box is the meeting point of the gas (from the cylinder) and the injected sample compound. The temperature of the inlet is kept high so that if the sample compound is in Liquid or Solid form it can be changed into Gaseous form.

B) Gas column Further, the gaseous mixture of inert gas and sample compound is introduced to the capillary column. The column is a narrow tube-like structure usually made up of stainless steel or glass. This column is usually 15-30 meters long. The column is filled with stationary phase mostly liquid or sometimes solid. The stationary phase only with a high boiling temperature suitable as the temperature of the oven is around 300 degrees Celsius. Liquid with low boiling temperature will change into gaseous form and the chromatography process will fail as we need two different phases.

D) Molecule exiting the column and Oven At the column end, a detector is placed, the molecule with less boiling or less molecule size would reach here earlier than the other. The detector is connected to a computer for analysis. The less boiling point molecule would create a peak on the computer. The molecule with high temperature would take time so to increase the efficiency the oven temperature is increased and they mark another peak on the computer. The process of changing the temperature to control the time rate is known as Time programming.

E)Calculation A graph between retention time and intensity is made for both two peaks and use to detect the compound. As this method doesn’t ensure the correct detailing so we used Mass Spectrometry in the detector to ensure that the results are correct.

The main role of a gas capillary manufacturing unit is to figure out all the pros and cons, to conclude and reach the quality required to assist with day-to-day needs.

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