What is Gas Chromatography

This post provides basic information about what is gas chromatography, construction and working of gas chromatography and finally some applications of gas chromatography.

Definition of Gas Chromatography:

Chromatography is a physical method of separation of the compounds of a mixture by distribution between two phases out of which one is a stationary bed of large surface area and the other is a fluid phase which percolates through or along the stationary phase.

Construction and working principle of gas chromatography:

The basic gas chromatograph consists of following parts

  1. Carrier gas supply with pressure regulator and flow monitor

  2. Sample injection system.

  3. Chromatographic column

  4. Thermal compartment

  5. Detection system

  6. Strip chart recorder

Diagram of Gas Chromatography:

Gas Chromatography

Gas Chromatography

In gas chromatography, the carrier gas is stored in a cylinder at a controlled pressure. The carrier is stored in a cylinder at controlled pressure. The pressure regulator is fitted on the cylinder. This gas is passed to sample injection port at a fixed, controlled flow rate through a floe regulator. The sample injection port is maintained at a certain temperature T1. The temperature T1 is selected such that the rapid vaporization of solute takes place but it doesn’t have a thermal degradation.

The sample injector injects the gas/ liquid sample through syringe. The solute vapor mixes rapidly with the carrier gas and flows into the column. In the column, the different solutes in the vaporized sample are separated from each other depending upon their interaction with the column packing. The column is operated at temperature T2. The resolution efficiency obtained with a particular column is dependent of this temperature T2. A detector is placed at the end of the column. The separated solutes reach the detector individually.

The detector then produces the electrical signals corresponding to each solute quantity in the sample. This detector output is connected to the strip chart recorder which plots the signals amplitude versus time. This plot is known as gas chromatograph. From this gas chromatograph the components of the mixture and their concentration is identified.

A typical gas chromatograph is as shown below:

strip chart gas chromatograph

strip chart gas chromatograph

Gas chromatography Applications:

  1. Using gas chromatography, substances that vaporize below ca. 300 °C (and therefore are stable up to that temperature) can be measured quantitatively.

  2. Gas chromatography can be used to analyze content of chemical product like measuring the quality of products in the chemical industries.

  3. It can also be used for measuring toxic substances in soil, water or air.

  4. Gas Chromatography is used extensively in forensic science.

Related topics:

Liquid chromatography
Gas chromatography
Liquid Chromatograph (HPLC)
Flame ionization detector

Watch following video to understand what is gas chromatography? and Working principle of Gas chromatography. what is Gas chromatography gcse?


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