Explain chromatographic methods to refine the elements.

Principle: The method is based on the difference in adsorption of different components of a mixture on an adsorbent.
The mixture is placed onto a stationary phase,which may be a solid or a liquid. $A$ pure solvent,a mixture of solvents,or a gas is allowed to move slowly over the stationary phase. Different components of the mixture get separated gradually as the moving phase progresses. There are several chromatographic techniques such as paper chromatography,gas chromatography,thin-layer chromatography,and column chromatography. Column chromatography is very useful for the purification of elements that are available in minute quantities and where the impurities do not differ significantly in chemical properties from the element to be purified.