How does solubility affect chromatography?

In paper chromatography, for example, you dissolve the components of a mixture in a solvent.

As the solution moves along the paper, the various constituents travel at different speeds. They separate into different spots.

The separation depends on the different attractive forces between the paper and the components of the mixture.

The components are constantly moving back and forth between the paper and the moving solvent.

An analogy is a fast-moving river that is carrying trapped swimmers to a waterfall in the distance.

The swimmers grasp desperately at the many tree branches and stumps, but they eventually lose their grip and are carried along to another branch.

The swimmers with the weaker grip spend more time being carried along by the water and will meet their deaths more quickly.

The swimmers with the stronger grip can hold on longer. They spend less time being carried along the water, so they are carried to their deaths more slowly.

The more time a component stays in the solvent, the faster it moves along the paper, because the solvent is moving forwards.

The components that are strongly attracted to the paper spend less time in the solvent and move more slowly.

Thus, the components separate into separate spots, based on their different attractions to the paper.

Here is a video showing a paper chromatography experiment that was conducted to separate the pigments in a black marker.

Video from: Noel Pauller