Chromatography has evolved from paper chromatography to TLC and from chromatography to instrumental techniques such as GC and HPLC. Gas chromatography (GC) is the important analytical method for the separation of volatile compounds in a mixture by injecting a liquid or gaseous sample into a mobile phase, usually called a carrier gas, and passing the gas through a carrier phase stationary. The mobile phase consists of an inert gas which can be nitrogen, helium or argon and whose column can be packed or capillary, which can be available in different diameters and lengths according to the needs of the application. 'sample.
This type of chromatography isolates analytes based on the volatility of the analytes. The more volatile compound will separate quickly, while the less volatile compound will be gradually removed from the column. Gas chromatography follows the principle of separation of volatile compounds with a mobile phase and a stationary phase.
Several detector options are available with high sensitivity to detect a wide range of samples not possible with other chromatographic techniques. The different types of GC detectors are Flame Ionization Detector (FID), Thermal Conductivity, Nitrogen Phosphorus, Photoionization, Electron Capture, Flame Photometry, Electrolytic Conductivity Detector, and Mass Spectrometer , etc.
Advantages of Gas Chromatography (GC):
- The main advantage of gas chromatography is its high sensitivity, resolution and separation capacity, which allow 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 pharmaceutical and other applications.
- Gas chromatography can analyze a sample much faster than other chromatographic techniques.
- It is a robust separation method that provides superior signal-to-noise ratio.
- Only a very small amount of sample needs to be injected and its detectors are extremely sensitive, allowing it to detect extremely low concentrations (ng-pg).
- Depending on the molecule needs, different types of GC columns are available in many diameters and lengths.
- Gas chromatography is simple, automated, and allows rapid data analysis that offers relatively high accuracy, precision, and reproducible results.
- Operating parameters such as flow, temperature and pressure, etc. are easy to modify even during chromatographic tests.
Disadvantages of a Gas Chromatography (GC):
- The main disadvantage of GC is that only volatile and thermally stable compounds can be separated by gas chromatography.
- The detectors used in the GC are destructive, except MS.
- The selectivity in HPLC or TLC is also better, because a mobile phase can be easily changed. In GC you can only change the temperature of the column and the oven, but you cannot change the mobile phase because you have a constant flow of carrier gas (helium, nitrogen).
- Since hydrogen gas, which is used for the flame, is highly flammable, care should be taken when using it.
- It is not possible to recover the individual components of the sample.
The most frequently asked questions about gas chromatography are as follows.
What is the advantage of gas chromatography over liquid chromatography?
The main advantage of gas chromatography over liquid chromatography is that, compared to high performance liquid chromatography, the length of the GC column is longer, allowing the separation of more complex sample mixtures with a high resolution.
What is the advantage of GC over TLC?
The main advantage of GC over TLC is that GC is an automated quantitative technique where the software can provide accurate data such as peak area, resolution, wear factor and height etc. While TLC only separates compounds and is not intended 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 surface of the metal, and in GC-MS it can reduce the efficiency of the turbomolecular vacuum pump. These are some disadvantages of hydrogen in GC.
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