Chromatography is used to separate mixtures of substances into their components. All kinds of chromatography work on precisely the exact same principle. All of them have a stationary phase a good, or a liquid supported on a solid and a mobile phase a liquid or a gas. The mobile phase flows through the stationary phase and conveys the parts of the mix with it. Various components travel at different prices. We will examine the reasons for this farther down the page. In paper chromatography, the stationary phase is a really uniform absorbent paper. Sometimes, it might be possible to create the stains visible by reacting them with something that produces a colored product. A fantastic example of this is in chromatograms generated from amino acid combinations. Suppose you had a mixture of amino acids and wanted to find out Which particular amino acids that the mixture contained.
A little drop of a solution of the mixture is put on the base line of this paper, and similar modest areas of the amino acids are put alongside it. The paper is then stood in a suitable solvent and left to grow as before. From the diagram, the mix is M, and the amino acids are labelled 1 to 5. The job of the solvent front is marked in pen and the chromatogram is permitted to dry and is then coated with a solution of ninhydrin. The next diagram shows what it might look like after spraying with ninhydrin. Although paper chromatography is easy to do, it is fairly tricky to describe compared with thin layer chromatography. The explanation is based to some degree on what type of solvent you are using, and lots of sources gloss over the issue completely. When you have not already done so, it would be useful if you could read the explanation for how thin layer chromatography functions link below.
Suppose you use a non-polar solvent like hexane to develop your chromatogram. Non-polar molecules in the mix which you are attempting to separate will have little attraction for the water molecules attached to the cellulose, and so will spend most of their time dissolved in the transferring solvent. Molecules such as this will travel a ways up the paper carried from the solvent. On the other hand, polar molecules will have a High fascination for the water molecules and less for the non-polar solvent. They will therefore tend to dissolve in the thin layer of water around the cellulose fibers a lot more than at the moving solvent. Since they spend more time dissolved at the stationary phase and less time in the mobile phase, they are not likely to travel very fast up the newspaper. The trend for a compound to split its time between two immiscible solvents hexane and water that will not mix is called partition. Paper Chromatography with a non-polar solvent is therefore a sort of partition chromatography.