Chromatography is a analytical technique that is widely used for separation, Isolation and identification compounds. Such as organic matter such as amino acids, starch, pigments for vitamins and plants, etc.
This technique was introduce by M. Tswett. M. Twett was russian botanist. In 1906 he introduced this technique. He employed chromatrographic technique to separate various plants pigments. Such as chlorophyll’s and xanthophyll’s and several other colored substance by passing solution of these compounds ,through a glass column packed with finely divided calcium carbonate.
The column of calcium carbonate was an adsorbent. The different compounds were absorbed at where extents. This gives rise to co-loured bands at different positions of the column.
Tswett called this system of co-loured bands as the chromatogram and the method is chromatography.
The calcium carbonate column used in the method used by Tswett remains stationary. Therefore referred to as the stationary phase.
The solution of the vegetable extract moves down the column. Therefore known as the mobile phase.
Definition of chromatography:
A physical method of separation of a mixture of solutes brought about by dynamic partition or distribution of dissolved materials between two immiscible phases.
One of which is called the mobile phase and other one is called the stationary phase.
The chromatographic methods of separation, involve in the following steps:
- Adsorption or retention of a substance.
- Separation of the adsorbed substances by the mobile phase.
- Recovery of the separated substance by continuous flow of mobile phase. This method is known as elution.
- Qualitative and quantitative analysis of the eluted substances.
Classification of chromatographic method:
This method can be classified in three ways:
- Classification based on the physical state.
- Classification based on the contact between the mobile phase and stationary phase.
- On the chemical or physical mechanism.
Classification based on the physical state:
The first method based on the physical state of the mobile phase and the stationary phase. They fall into four categories , Such as
Classification based on contact between mobile phase and stationary phase:
This is a second method of classification :
- Liquid-solid chromatography (LSC)
- Liquid-Liquid chromatography (LLC)
- Gas-Solid chromatography (GSC)
- Gas-Liquid chromatography(GLC)
Classification based on Chemical or physical mechanism:
The third method of classification that is based on the physical and chemical mechanism.
- Column chromato-graphy
- Ion – exchange chromatography
- Paper chromato-graphy
- Gas -liquid chromato-graphy
- Gas chromato-graphy
- Thin layer chroma-tography