Solvent Systems:
The nature of solvent plays an important role in the development of paper chromatogram. A solvent should be free from impurities and dried before use. Polar phase such as water is absorbed by the paper and held stationary whereas the less polar solvent such as ethanol, acetone, glycol, formamide, acids, and amines flow through easily. Though pure solvent may be used but a mixture of solvents is preferred. Many solvent mixtures can be used provided these are not immiscible with one another. The following criteria may be adopted for the choice of the solvent;
- The solvent shall not react chemically with any of the components of the sample mixture.
- The composition of solvent mixture should not change with time. It means that none of its components should be volatile.
- The solvent shall not interfere along with the detection of spots.
- An distribution ratio should be independent of solute concentration.
- The minimum difference between the Rf values of any two components should be 0.05 or 0.1 so that they may be separated easily.