Chromatography has evolved, from paper chromatography to TLC and chromatography to instrumental techniques including GC and HPLC. Gas chromatography (GC) is the significant analytical method for the separation of volatile compounds in a mixture by injecting a liquid or gaseous sample into a mobile phase, usually called the carrier gas, and passing the gas through a stationary phase. The mobile phase consists of an inert gas it may be nitrogen, helium, or argon and the column can be packed or capillary they can available in different diameters and lengths as per the requirement of the sample.
This kind of chromatography isolates analytes based on the volatility of analytes. The more volatile compound will be separated rapidly, whereas the less volatile compound will gradually be eluted from the column. The gas chromatography follows the principle of the partitioning of volatile compounds with mobile phase and stationary phase.
Several detector options are available with high sensitivity, to detect a wide range of samples that is not possible with other chromatographic techniques. The different types of GC detectors are flame ionization (FID), thermal conductivity, nitrogen phosphorous, photo-ionization, electron capture, flame photometric, electrolytic conductivity detector, and mass spectrometer, etc.
Advantages of gas chromatography (GC):
- The major advantage of gas chromatography is its high sensitivity, resolution, and separation ability, which allows it to separate a wide range of volatile compounds.
- It can be upgraded to a mass spectrometer (MS), which is used to determine the mass-to-charge ratio of ions.
- It comes with a variety of detectors and injectors that can be used for various pharmaceuticals as well as other applications.
- Gas chromatography can analyze a sample much faster than other chromatographic techniques.
- It is a robust method of separation that gives the superior signal-to-noise ratio.
- It only takes a very small amount of sample to inject, and its detectors are extremely sensitive, allowing it to detect extremely low concentrations (ng-pg).
- As per the requirement of the molecule, there are different types of GC columns are available in many diameters and lengths.
- Gas chromatography is easy, automated, and has quick analysis of data which gives comparatively high precision, accuracy, and reproducible results.
- Operational parameters such as flow rate, temperature, and pressure, etc. are easy to change even during chromatographic runs.
Disadvantages of a gas chromatography (GC):
- The major disadvantage of GC is that only volatile and thermally stable compounds can be separated using gas chromatography.
- Detectors which are used in the GC are destructive, except for MS.
- Selectivity in HPLC or TLC is also better as a mobile phase can be easily changed. In GC, you can just modify the temperature of the column and oven, but you cannot change the mobile phase as it has a constant flow of carrier gas (helium, nitrogen).
- Since hydrogen gas, which is used for flame, is highly flammable, care must be taken when using it.
- It is impossible to recover individual sample components.
Commonly asked questions on gas chromatography are as follows.
What is the advantage of gas chromatography over liquid chromatography?
The major advantage of gas chromatography over liquid chromatography is that, as compared to high-performance liquid chromatography, the column length of GC is longer, allowing for the separation of more complex sample mixtures with high resolution.
What is the advantage of GC over TLC?
The major advantage of GC over TLC is that the GC is an automated quantitative technique in which software can offer precise data such as peak area, resolution, tailing factor and height, etc. Whereas TLC is only separates the compounds and is not for quantitative analysis.
What are the disadvantages of hydrogen in gas chromatography (GC)?
It can decrease the resolution of the chromatogram, hydrogen can react with unsaturated components on the metal surface, and in GC-MS it can reduce the efficiency of turbo molecular vacuum pump these are some disadvantages of hydrogen in GC.
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THanks very helpful
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