How is paper chromatography performed?

Paper chromatography is performed by placing a spot of solution or sample on a strip of absorbent paper and allowing a solvent to move up the strip.

In more detail, paper chromatography is a method used to separate mixtures into their individual components. The process begins by drawing a line near the bottom of a sheet of absorbent paper, such as filter paper. This is known as the baseline. A small spot of the solution or sample to be tested is then placed on this line. The paper is then placed in a container with a shallow layer of a suitable solvent, such as ethanol or water, ensuring that the baseline is above the level of the solvent.

The solvent slowly moves up the paper, carrying with it the components of the mixture. As the solvent travels, it takes the components of the mixture along with it. Different components travel at different rates, depending on their solubility in the solvent and their attraction to the paper. This results in the components being spread out at different distances from the baseline, effectively separating them.

Once the solvent has nearly reached the top of the paper, the paper is removed from the solvent and allowed to dry. The different components of the mixture will have travelled different distances up the paper, and these distances can be used to identify the components. This is often done by comparing the distances travelled with those of known substances under the same conditions.

In some cases, the components of the mixture may be colourless and therefore not visible on the paper. In such cases, a locating agent can be used. This is a chemical that reacts with the components to produce a coloured product, making the spots visible.

Overall, paper chromatography is a simple, yet powerful technique for separating and identifying the components of mixtures.