Chromatography is a laboratory technique which is frequently employed for the separation of mixtures. In this technique, the mixture that must be separated is first dissolved into a fluid (commonly referred to as the mobile phase). This fluid carries the mixture through a different structure (commonly referred to as the stationary phase). The fluid carries different components of the mixture at different speeds. Therefore, the components of the mixture are separated in the stationary phase of the chromatography setup. An introduction to the classification of chromatography based to different criteria is provided in this article.
Classification of Chromatography based on the Chromatographic Bed Shape
- Column Chromatography: In this type of chromatography, the stationary phase of the setup is placed inside a tube. Then, the particles of the stationary phase (which is in the solid state) are made to fill the inside with the tube. An unrestricted, open path is then prepared for the mobile phase (somewhere along the middle of the tube).
- Planar Chromatography: In this type of chromatography, the stationary phase of the apparatus usually has a planar shape. Different subcategories of planar chromatography include paper chromatography (where the stationary phase is a special type of paper) and thin layer chromatography (usually abbreviated as TLC).
Classification of Chromatography based on the Physical State of the Mobile Phase
- Gas Chromatography: In this type of chromatography, the mobile phase is a substance that exists in the gaseous state. It can be noted that gas chromatography is also known as gas-liquid chromatography, and is often abbreviated to GLC. This type of chromatography almost always involves the use of a packed column.
- Liquid Chromatography: This type of chromatography involves the use of a mobile phase that exists in the liquid state. Liquid chromatography, often abbreviated to LC, can be carried out either on a plane or in a column. It can be noted that there exist many subcategories under liquid chromatography such as high-performance liquid chromatography and reversed phase liquid chromatography.
Classification of Chromatography based on the Mechanism of the Separation
- Ion Exchange Chromatography: This type of chromatography is also known as ion chromatography. Ion exchange chromatography involves the separation of the components of the mixture via an ion exchange mechanism. Differently charged components of the mixture are separated with the help of different ions in this separation technique.
- Size Exclusion Chromatography: This type of chromatography involves the separation of different components of the mixture based on their sizes. In size exclusion chromatography, components of the mixture are filtered based on their hydrodynamic volume or hydrodynamic diameters. It can be noted that size exclusion chromatography is also known as gel permeation chromatography or gel filtration chromatography.
- Expanded Bed Adsorption Chromatography: This type of chromatography is commonly used for biochemical separation processes. It is a specialized technique which is used for the capturing of proteins from the mixture sample.
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