Chromatography

Chromatography is a chemical-based technique that is used for the separation and purification of chemically formed mixtures into separate individual compounds. The word Chromatography was derived from the techniques used in the 19th century to separate pigments from compound mixtures. There are various types of chromatography that are used in labs, such as thin-layer chromatography, gas chromatography, column chromatography, etc. 

Principles of Chromatography 

Chromatography is used by every organic chemist and every biochemist. Therefore, before moving down to the principle of chromatography, it is pertinent to understand the terms used in chromatography.

1. Analyte: This is the mixture whose components needed to be individually separated and further analysed.

2. Elute: This is the fluid that enters the column.

3. Elution: This is the process of washing out the mixture with the help of a suitable solvent. 

4. Eluate: This is the fluid that enters the column and gets collected in the flasks.

5. Carrier: This is a solvent that moves through the column.

6. Adsorbent: This is the fixed substance inside the column. 

So, the Chromatography is carried out in two different phases, the mobile phase and the contiguous stationary phase. The stationary phase is either liquid or solid, whereas the mobile phase is either gas or liquid. 

In the chromatography, the compound mixture moves inside the column with the mobile phase & through the stationary phase and gets separated depending upon the different degrees of adhesion of each individual component in the mixture. 

Types of Chromatography 

Mainly there are four types of chromatography, which are as follows:

Thin-layer chromatography:

This is the most commonly used chromatography method used in chemist and biology labs. In this type of chromatography, a thin layer of silica is used as a stationary phase on glass, metal or any rigid substance. The component which seeks to be separated is placed on the chromatography in the form of small drops or in a line and it is placed into a sealed container. Thereafter the solvent rises up along with all the components of the compound mixture. 

These components travel with the solvent depending upon their polarity. In this type of chromatography, non-polar components travel faster compared to the polar component. Thus, in last the separated components can be observed under UV-Light. 

Column Chromatography:

In this method, silica or alumina is placed as a stationary phase and a suitable liquid is taken as a liquid phase. Column chromatography is also a separation technique used to separate individual components from a chemical mixture using a column of adequate adsorbent packed in a glass tube. The column is packed with silica or alumina. The individual component gets separated from the mixture depending upon the polarity of molecules.

Paper chromatography:

The paper chromatography technique is similar to thin-layer chromatography. However, in this technique, a specially formed chromatography paper is used instead of silica. This chromatography paper is made up of cellulose, the mixture is placed on the paper in form of either drops or lines. The non-polar components move at a faster rate in chromatography and the polar compounds attach with the cellulose and it does not let it go any further.

Adsorption Chromatography:

In this technique, the mixture is absorbed on the adsorbent at different degrees as per the absorptivity of different individual components. The mobile phase is carried out over the stationary phase that carries the individual components upwards. 

Application of Chromatography

Chromatography is recognised as a technique for the separation and purification of organic and non-organic substances. This technique has also been found useful in the fractionation of complex mixtures, separation of too closed compounds for example isomer and unstable substances. 

Chromatography has played an important role in the usage of pharmaceuticals. Pharmaceutical labs use chromatography to measure and analyse compounds for contaminants. Chromatography techniques can ensure to these labs that the safety component is separated from the dangerous form. 

The chromatography technique is also used by premier restaurants and hotels to control the quality of the food and beverages.  Chromatography is used to determine the expiry date of any product by analysing the number of organic acids present in the particular food product. 

Conclusion 

The principles of chromatography have a vast usage in the field of laboratories, chemists and biologists. The reason behind this vast usage is its simple principle and the technique is simple in use which does leave some room for substantial refinement.