Paper chromatography
Paper chromatography is an example of partition chromatography. The stationary phase is the water molecules present in the pores of the paper. The mobile phase is a solvent or a mixture of solvents, such as hexane, acetone, toluene, or a methanol-water mixture.
The components in the sample mixture are separated by partitioning of the components between the stationary phase and the mobile phase. The strength of interaction with the stationary and mobile phases will be different for each component. Therefore, the components will move at different rates along the sheet of paper as the mobile phase moves. The retardation factor represents the characteristic rate of movement of a component as the mobile phase moves.
The mobile phase moves through the paper by capillary action. There are four types of paper chromatography and these depend on the movement of the mobile phase. These are:
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Ascending: The mobile phase moves up the paper
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Descending: The mobile phase moves down the paper
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Circular: The mobile phase moves from the middle of the circle outwards
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Two dimensional: The mobile phase is run in 2 directions, one after the other.
The resultant piece of filter paper, after running the solvent, is the chromatogram. If the components are colored, then it will be easy to locate the spot on the paper. However, if the component is colorless then a developer will be required.
Paper chromatography experiments:
References:
- NCERT Chromatography handbook