Chromatographic techniques

What Chromatography Is, and Where the Name Comes From

Chromatography is a technique used both to separate the components of a mixture and to purify individual compounds. Its name comes from the Greek word chroma, meaning colour — the technique was first discovered in 1903 by Tswett, who used it to separate the coloured components found in plants.

The Underlying Principle

The principle behind chromatography is similar to that of solvent extraction — the distribution of solutes between two phases. In chromatography, these two phases are called the stationary phase and the mobile phase. The technique relies on the fact that different components of a mixture move through the stationary phase at different rates under the influence of the mobile phase. The mixture is first loaded at one end of the stationary phase, after which the mobile phase — a pure solvent or a mixture of solvents — is allowed to move over the stationary phase. Depending on how strongly each component is attracted to the stationary phase versus the mobile phase, it either lingers on the stationary phase's surface or travels along with the mobile phase, and the components gradually separate from one another as a result.

The Two Main Types …