Introduction to paper chromatography:
Paper chromatography separation technique of analytical chemistry, which separates the mixture of analytes with the help of the mobile phase on a sheet of special paper that acts as a stationary phase. The process of paper chromatography is parallel to thin layer chromatography, so it is also used to teach the TLC process.
The principle of paper chromatography:
All chromatography techniques adhere to the same principle. According to other chromatography techniques, paper chromatography consists of a mobile phase and a stationary phase. The paper is used as a stationary phase and the solvent is used as a mobile phase. The mixture of sample component travels with the mobile phase through the stationary phase and get separated on the sheet of paper due to their difference in affinities towards the stationary phase.
The stationary phase of paper chromatography:
Paper chromatography is parallel to TLC, the contrast is that the rather than utilizing a thin layer of silica on a sheet of metal, a special kind of paper that is used as a stationary phase. This paper is composed of cellulose and contains polymers -OH functional groups. The other kinds of papers are also used in paper chromatography like silica and alumina impregnated papers, acetylated papers, and silicone oil-impregnated papers.
The process of paper chromatography:
In this chromatography, a special quality paper used as a stationary phase is called chromatography paper. The mobile phase is a solvent or mixture of solvents (e.g. Methanol, water, etc.). A sample solution of a complex mixture is spotted on a line approximately 2 cm above the paper, and after that suspended in the appropriate solvent in the chromatography chamber. The solvent rises-up and flows over the spot by capillary action. Paper selectively holds different analytes in two phases as per their different partition. The developed paper strip is called a chromatogram. The spot of different colored compounds appears on different heights from the initial position on the chromatogram. The spot of different colorless components can be seen either using a suitable spray reagent (e.g. Ninhydrin reagent) or under ultraviolet light (e.g. UV cabinet). The relative adsorption of separated components is expressed as a retention factor (Rf value).
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