Module 3: Analysis

What is chromatography?

Chromatography is an analytic technique used to separate the components in a mixture.

How does chromatography work?

Phases

During chromatography, a mobile phase sweeps a mixture over a stationary phase. the stationary phase is fixed to the plate and the mobile phase moves in a definite direction.

Chromatography works on the basis that different components have different affinities for a stationary phase and for the mobile phase. The stationary phase interacts with the components in the mixture, slowing them down. The greater the interaction, the more the components are slowed down. This allows different components to flow over the stationary phase at different phase at different speeds, separating the components.

Separation

Efficient separation depends on two main factors.  A solid stationary phase separates by adsorption. As the mobile phase passes over the stationary phase, component molecules are able to bind to the solid making up the stationary phase. This happens at the surface of the stationary phase. A liquid stationary phase separates by relative solubility. Some components dissolve more readily in the liquid and these are slowed down more than components with lower solubility.