What chromatography is for

The chromatography had its beginnings in 1906, when the Russian botanist Mikhael Semenovich laid the advantages of chromatography. In that year Semenovich published two papers, in which he describes his experience in separating components of egg and leafy yolk extracts.

The term chromatography was due to the colorations of pigments that the Russian botanist observed in his investigations. This word comes from “chrom” (color) and “graphe” (writing), which would mean writing in colors.

If you want to know more about what chromatography and its types are, we invite you to read this article where you will learn about the different types of chromatography, applications and other data.

What chromatography is

Chromatography is a method of separating substances from a mixture of compounds. The sample to be analyzed will interact with two phases (a stationary phase and a mobile phase) continuously until the separation of the compounds is carried out.

Statary phase

The stationary phase could be a solid or a liquid, which will remain fixed in its initial position. Depending on the type of chromatographic technique, the type of stationary phase will be chosen, for example, in a gas chromatography, the stationary phase can be a solid or liquid and, on the contrary, in the chromatography of ion exchange, the stationary phase is a solid.

Mobile phase

The mobile phase could be a liquid or a gas that will cross on a surface and by the stationary phase. The components of a mixture are dissolved in the mobile phase. In the case of gas chromatography, the mobile phase will be a gas and, on the other hand, in the chromatography of ion exchange, the mobile phase will be a polar liquid.

What chromatography is for

Chromatographic techniques serve to separate compounds from a mixture. In addition, it also serves to identify and determine chemical compounds in a sample.

Once the process has been carried out and the mixture compounds are separated, we will want to know what chemical compound it is, which is why the retention or delay factor (Rf) will be calculated. The retention factor is used in thin layered chromatography, and is defined as the relationship between the distance that travelled the substance and the distance travelled from the solvent front.

For example, if the substance went through 3 cm, and the solvent front is 10 cm, then the retention factor is 0.30. Through this factor we will be able to know which compounds are present in the sample and also which of them is the most and least polar.

Types of chromatography

There are different types of chromatography, and each of them works in a specific way. Here are some types of chromatography:

Distribution chromatography

Distribution chromatography is a widely used technique, which is done on strips of filter paper, or on plates covered with an adsorbent material. Regarding the separation of the substances present in the sample, this is based on a distribution by adsorption and capillarity. At the end of the process, the differences in solubility that exist between solutos will be evident.

Ionic exchange chromatography

Resins are used in this type of chromatography that will retain the solutes by electrostatic attraction. The stationary phase are resins that are loaded only and will be responsible for retaining the counterions present in the mobile phase, and exchanging it. An example of the use of ion-exchange chromatography is the separation of organic and inorganic ion substances.

Paper chromatography

Paper chromatography is a relatively simple technique used since ancient times, and is used to separate and identify polar compounds such as vegetable pigments, organic acids, amino acids, carbohydrates, etc. Regarding phases, a cellulose paper is usually used as a stationary phase; and a polar liquid as a mobile phase. The advantage in this type of chromatography is that small amounts of samples can be used, for example in micrograms or milligrams.

Sketron in thin layer

It is a simple and fast technique, which is often used in organic chemistry laboratories. The process consists of the separation by migration of the components of a sample, through a thin adsorbent layer. In this type of chromatography the stationary phase will have to be deposited on a support, such as glass or aluminum, and the mobile phase will ascend throughout the stationary phase thanks to capillaryity.

Examples of chromatography

Here are some examples of chromatography:

  • Determination as a percentage of the solvent in an agrochemical product.
  • Determination of active substances in a medicine.
  • Quality tests of the purity of solvents used as a raw material to a plant.
  • Quality tests of raw materials entering factories of medicinal products, such as isopropyl alcohol, paracetamol, camphor, etc.
  • Quality tests of food products such as flavourings and dyes.
  • Analysis of biological samples (blood, urine, soil samples, etc.).
  • In adhesive factories they are used for testing the control of the amounts of solvents, dyes, emulsifiers, etc.
  • In wine production, it is used to measure the parameters of the concentration of components, amine analysis, etc.
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