2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16
Gas chromatography is a method of analysis that has received a very good theoretical development. It is the careful study of its theoretical and practical foundations that has contributed to the rapid development of this technique in recent decades.
It is known that gas chromatography differs from other similar methods in that it uses gas as a mobile phase. The stationary phase may be a solid or a liquid. Depending on this, one speaks of gas-adsorption or gas-liquid chromatography.
Separation of mixtures of substances in devices such as a gas chromatograph occurs due to repeated repetition of the process of distributing components between a stationary liquid or solid phase and a moving gas. The separation process is based on the difference in volatility and solubility of the analyzed substances. The component with the highest volatility at a given temperature and the lowest solubility of the stationary phase will move faster through the column.
The use of gas as a mobile carrier provides advantages such asclarity of separation of constituent substances and the speed of analysis. The test sample is introduced into the column in gaseous or vapor form. Using this method, it is possible to analyze not only gases, but also liquid and solid substances, which are transferred to the required state by heating. In this regard, in gas chromatography, the temperature at which the entire process takes place plays a very important role. The performance limits for the gas-adsorption method of analysis range from 70 to 600°C, and for gas-liquid - from 20 to 400°C. The industry produces a gas chromatograph that allows you to pre-program the temperature.
This method makes it possible to analyze substances whose molecular weight is less than 400. They do not decompose during evaporation, and do not change their composition during subsequent condensation.
Mostly used in analytical practice is gas-liquid chromatography. Compared to gas adsorption, it has some advantages, which are mainly associated with a wide choice of possible stationary liquid phases, as well as high purity and, quite importantly, uniformity of liquids.
Gas Chromatography is a rapid method with high accuracy, sensitivity and automation capability. The versatility and flexibility of this method determines the device used in a particular case. Gas chromatography, used for quantitative analysis, gives unambiguous results that are not in doubt.
This method allows you to solve manyanalytical problems, separate and determine the ratio of compounds with a minimum difference in vapor pressure. The gas chromatography method is used to purify chemicals, splitting mixtures into individual components. It is especially effective in separating substances of similar composition that belong to the same class: organic acids, alcohols, hydrocarbons.
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