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Dec 10, 2023

What is liquid chromatography?

By Paul Heney | January 23, 2023 Chromatography is a common laboratory technique

By Paul Heney | January 23, 2023

Chromatography is a common laboratory technique used to separate a mixture into its individual components, or fractions. This can allow the components to be identified and quantified. The first stage in chromatography is to dissolve the mixture in a fluid solvent, which may be either a liquid or a gas. The fluid solvent is known as the mobile phase. When a liquid solvent is used as the mobile phase, the technique is known as liquid chromatography.

Once the mixture has been dissolved into the mobile phase, it is passed through a system which may consist of a column, a capillary tube, a plate, or some combination of such items. This system is known as the stationary phase and is designed to present surface sites at which the constituents of the mixture interact. Because of differences in the way constituents in the mixture will interact with the surface sites, they move a different speeds, causing separation along the stationary phase. Typically these differences are based on the affinity of substances for the surface material, but separation may also be based on particle size (size exclusion) or charge (ion exchange).

Liquid Chromatography may be classified according to the shape and configuration of the stationary phase:

Multiple stationary phases may be used sequentially. So, for example, column chromatography may be initially used for bulk separation and the obtained fractions then applied to thin-layer chromatography.