What is the principle behind the use of paper chromotography in the separation of mixtures?

Question

What is the principle behind the use of paper chromotography in the separation of mixtures?

Answer 1

Properties of paper and that of compounds allow compounds to travel up paper at different speeds. Compounds (polar) whose properties match that of the paper (polar) travel slower than those whose properties are different (less polar) from the paper.

Answer 2

I've actually done this in chemistry lab already, the point in the beginning is to have the paper absorb a solution to a certain point where the solution ends up interacting with the samples on the chromotography. Then the chromotography is viewed under an  ultraviolet machine in order to observe how many times a substance has separated itself up a strip of paper. The point of doing this is to separate mixtures into a pure form. A sample that only goes through one or no separations is pure on its own, a sample that goes through several separations is a mixed and impure sample.

Answer 3

The biggest principle?  Polarity.

Usually, in your mixture, you will have substances with different polarities. The paper itself is relatively polar; the running solvent is relatively nonpolar.  As the solvent is running up your paper, it will start to take the substances in your mixture with it.  Since like interacts with like in the polarity world, nonpolar substances tend to be taken farther up the paper by the solvent, while polar substances do not go as far.  The substances that go the farthest up are generally the most nonpolar.  This is why using water as a running solvent is generally a bad idea - you need something with some nonpolar poperties to effect a clean separation.