Paper Chromatography

Paper Chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be coloured, especially pigments. This can also be used in secondary or primary colors in ink experiments.

Procedure of Paper Chromatography:

1. Draw a pencil line on a piece of chromatography paper about 2cm from the end of paper.

2. Put a tiny spot of sample on the pencil line. Allow the spot to dry. Repeat by dripping the sample on the same spot.

3. Place a chromatography paper inside a glass tank with a small volume of ethanol. Ensure the sample spot is about 1cm above the level of ethanol.

4. Remove the chromatogram when the solvent front reaches nearly to the top of the paper.

5. The components will travel at different rates over paper depending on their solubility in the solver or their ability to be adsorbed on the chromatography paper.

6. In general, when a component is very soluble in the solvent and is weakly adsorbed by the paper, the faster it would move with the solvent and appear further up the paper.

It will be something like this:

As for the R_f (Retention Factor) value, it is a measure of the relative distance travelled by a component with respect to the solvent. It is found by the distance moved by the spot of the substance over distance moved by the solvent font.

If the melting point and boiling point of a substance decrease and increase respectively, this means that the substance is impure. The purity of a substance is very important as it is not safe for human to consume unpure stuffs.