What are the different types of chromatography?

Chromatography is a technique that separates components from complex mixtures on the basis of their size, structure, charge, binding affinities, and other properties. There are several different types of chromatography:

Liquid Chromatography

Liquid chromatography utilizes liquids that may incorporate hydrophilic, insoluble molecules. It is widely used to analyze organic compounds and metal ions in solutions, and to test water samples in pollution studies. 

Gas Chromatography

This technique uses helium to carry a gaseous mixture through a column of absorbent material. Identification of components in the mixture is based on the time taken to emerge from the column. Gas chromatography is used extensively in forensics to analyze blood samples at crime scenes and fibers found on an individual’s body. It is also used to detect bombs at airports.

Affinity Chromatography

Affinity Chromatography is used to separate a protein of interest from other proteins by virtue of its specific binding properties to an immobilized ligand. It works on the principle that components of a mixture can be separated when only some components have an affinity towards the stationary phase of the system. The other components are then eluted with the mobile phase.

Paper Chromatography

Among the most commonly used types of chromatography, paper chromatography uses a strip of paper as the stationary phase. It is based on the varying degree of interaction between the molecules and the stationary phase. The solvents are pulled up through the paper by capillary action to separate the solutes.

Flash Chromatography 

In flash chromatography, the components are separated on the basis of their differential adsorption to the stationary phase. The stationary phase is made up of smaller sizes of gel particles and pressurized gas is used to drive the solvent through the column.

Thin-Layer Chromatography

Thin-layer chromatography is a quick and simple method used to check the purity of an organic compound. It is carried out by using an absorbent material on flat glass or plastic plates. Thin-layer chromatography is widely used in forensics to analyze the dye composition of fibers and to detect the presence of insecticide or pesticide residues in foods.

Ion-Exchange Chromatography

Ion-exchange chromatography is based on electrostatic interactions between charged protein groups and a matrix. The matrix is a solid support material that has an opposite charge to that of the protein to be separated.