A little history
Chromatography, from the Greek chroma (color) and grapho (writing), comprises a set of techniques that aim to separate mixtures based on the different interaction capacity of each component on / in other substances in solid or liquid state. That is, it consists of passing a mixture of substances or mobile phase, over a stationary phase that will delay the flow of the substances in the mixture, causing the mixture to move over it, at different speeds (according to the different interactions produced between the solutes of the mobile phase as they move around or over the stationary solid phase), the different components of the mixture separate.
1850 (Philipp Otto Runge)
This German painter observed that when depositing drops of coloring substances on blotting paper, differentiated colored areas were originated
The Russian botanist known as Tsvet coined the term "chromatography" through his initial experiments separating chlorophylls from plant tissues (mobile phase) on columns of calcium carbonate (stationary phase).
At the same time, Paul Karrer, in Zurich (Switzerland) and László Zechmeister, in Hungary were also developing advances in the study of plant pigments. According to some articles, it was a scientific contest where kindness and chivalry prevailed among the various scientists.
Getting into chromatography
Think of chromatography as a career and you will see that it is much simpler than it sounds. Waiting at the starting line, we have a mixture of compounds, either in liquid or gas, as if they were a group of runners together and grouped together. When the race begins, the runners are soon separated from each other because they have different abilities. In the same way, chemical compounds separate at different speeds on a stationary solid. The key is to remember that chromatography is a surface effect.
As the liquid passes through the solid (stationary phase) the molecules are adsorbed by the surface and temporarily retained. This effect is known as adsorption. Each compound is subjected to adsorption in a different way so it will be more or less retained in the solid phase.
Subsequently, these retained molecules are "eluted" or dragged by a liquid (mobile phase) and taken to a detector where it will give us a signal known as a chromatogram (Figure 1).