This is the simplest of all the methods. The paper or strip is suspended vertically into a closed jar containing a suitable solvent)(mobile phase). taking care that the dried spot region remains above the solvent.The solvent ascends through the fibres of the paper by capillary action.The rate of ascend is slow and decreases with time because of gravity. In this process, the components of the mixture separate because of their movement to different extents in the direction of flow.When the solvent has moved a suitable distance, the paper is removed from the chamber. The position of the solvent front is marked with a lead pencil and the strip is allowed to dry If the substances are coloured, they appear as separate spots. If the substances are colourless, they need to be sprayed with a locating reagent for detection. The development distance of a compound on the chromatogram is usually expressed by Rf values( retention relative front ).
Rf = Distance of spot of component from the original line _______________________________________
Distance of solvent from from the original line
Rf value does not exceed 1.00 and only two decimal places need to be determined. The polarity of the component affects the Rf values. An increase in the polarity lowers the Rf values and vice versa.