Separation and Analysis of Gas Mixtures by Gas Chromatography

Posted by JOHN Lipsky on July 31st, 2017

The achievements of gas chromatography as a method of separation of substances in combination with such modern means of qualitative analysis as infrared and mass spectrometry, chemical reactions, to some extent obscured the possibility of purely chromatographic identification based on the use of patterns linking retention with the structure and physicochemical properties of sorbates and stationary phases.

However, in recent years a new direction has developed, which can be termed precision Gas Chromatography, meaning an increase in the accuracy of not only quantitative determinations but also a measurement of retention values, which dramatically increases the reliability of group and individual identification of both pure compounds and components of complex Mixtures.

In addition, the concept of the chromatographic spectrum is developing as a collection of data that uniquely corresponds to a group of sorbates of a closed structure or to an individual compound. These successes allow us to consider gas chromatography as an independent method of qualitative analysis.

Terminology: Chromatography in general, by definition, Straining is a method of analysis in which the current of a liquid or gas causes the separation of substances from each other by their differential movement in a porous sorption medium. Gas chromatography is a method of separating the components transferred into a vapor state that is distributed between a fixed stationary phase and a moving phase of an inert gas.

Gas chromatography as a new method of separation of substances quickly became a powerful tool of analytical chemistry. It has found wide application in laboratories of chemical industry and in various fields of scientific research, but the possibilities of this method are far from exhausted.

Gas chromatography is a method for separating volatile compounds. The mobile phase is an inert gas (carrier gas) flowing through a stationary phase with a large surface. The mobile phase is hydrogen, helium, nitrogen, argon, carbon dioxide. The carrier gas does not interact with the substances to be separated and the stationary phase.

In gas chromatography on solid substances, the main mechanism determining the separation of a mixture into components is adsorption, and in gas-liquid chromatography, the distribution between the carrier gas and the stationary liquid is most important.

Chromatography is a method of separation and analysis of a mixture of substances, based on the different sorption of the components of the analyzed mixture with a certain sorbent. Separation is carried out in columns filled with silica gel, aluminum oxide, ion-exchange resins (ion exchangers), etc., or on special paper. Numerous techniques are known in which hydrocarbon separation and determination is carried out by gas chromatography, with non-volatiles preliminarily subjected to gas chromatography.

Due to the different probability of the components of the mixture (mobile phase), their zonal distribution along the sorbent layer (stationary phase) occurs- a chromatogram appears that allows to separate and analyze individual substances (the process is similar to a multistage rectification).

Reaction gas chromatography is a method in which substances in a reactor are converted to certain compounds more suitable for separation by gas chromatography. As the following examples show, reaction gas chromatography is successfully used to solve various analytical problems that cannot be solved with conventional gas chromatographic analysis.

Chromatographic analysis is a method of separation of substances. It is due to differences in their absorption abilities. Now several types of chromatographic analysis are used, including gas and paper chromatography, liquid chromatography, etc.

In one of the types of paper chromatography - circular-, the separated substance is applied as a drop in the center of a circle of filter paper. At the same point, a solvent is dripped from the pipette. It spreads uniformly in all directions, capturing with itself and the substance dissolving in it.