Chromatography

Various chemical analysis techniques can be used to help identify the chemicals present in reaction mixtures or give important information about the products of a chemical reaction.

Chromatography is an important analytical technique because it allows chemists to separate substances in complex mixtures. There are a variety of types of chromatography, which can be used in different contexts.

In chromatography, substances are separated as they travel in a mobile phase which passes through a stationary phase.

Different substances travel at different speeds, so some move further than others in a given time.

Paper chromatography

In paper chromatography, the stationary phase is a sheet of chromatography paper. The mobile phase may either be an aqueous (water-based) liquid or a non-aqueous (carbon-based) organic solvent.

An example of an organic solvent is propanone - which is the main chemical in nail varnish remover.

For each chemical in the sample, there is a dynamic equilibrium between the stationary phase and the mobile phase.

The overall separation depends upon how strongly attracted the chemicals are to the mobile and the stationary phases.

This produces a chromatogram where different samples can be compared to a reference material.

Chromatogram showing a comparison of a mixture of three substances