Why do pigments separate in chromatography

It's best to do this on both the left hand side, and right hand side, of the paper. Remove the chromatogram immediately. Allow the chromatogram to dry, then measure the distance travelled by each spot and by the solvent. Results Record your results in a suitable table. For example: Ink Spot colour Distance travelled by spot mm Analysis 1.

Evaluation Question Explain why the distances travelled by each spot were measured in mm, rather than in cm. Reveal answer up. A chromatogram showing the photosynthetic pigments of a grass. Harmful solvent. There are many examples of chromotography at youtube. This set-up shows two different pen inks.

Purpose: To identify plant pigments by separation and isolation of the pigments using thin layer paper chromatography. The distance traveled by a particular compound can be used to identify the compound. The ratio of the distance traveled by a compound to that of the solvent front is known as the Rf value; unknown compounds may be identified by comparing their Rf's to the Rf's of known standards.

Cut a strip of coffee filter or filter paper. Draw a horizontal line with a pencil not pen about half an inch from the bottom.

Number your plots of ink, and put the paper with the ink blots into a cup. Add solvent from your kit until it has reached the top of the paper, and cover the container so that the paper and the air in the cup are saturated with solvent. As the paper absorbs the solvent, the different components of the ink in the pen react differently to it. These different spots of ink will separate out, allowing you to see exactly what the components of the ink colors were. You can then use the pen to draw a picture to try to notice the different colored dyes that you identified in the chromatography.

The pen experiment is helpful in understanding how paper chromatography works, because you can see how pigments of ink separate. Whenever you do a chromatography experiment, the purpose is to separate the parts of a whole out; in this case, the whole was the pen dot and you were separating out the ink.

This works because certain pigments have a harder time being moved along the chromatography paper by solvents than others do. When a pigment is made up of larger molecules, it will not react with the solvent as much to move up the paper -- resulting in it appearing lower on the paper than other pigments with smaller molecules. Next, chromatography solvent is used to separate the mixture of pigments painted on the paper.

In the experiment pictured at left, the solvent used was comprised of nine parts petroleum ether and one part acetone. A small amount of this solvent is added to a large test tube and capped with a rubber stopper.

Note that chromatography solvent is highly volatile and flammable. The V-shaped tip of the paper is placed in the chromatography solvent and acts as a wick to draw the solvent up the paper, separating pigments according to their relative solubility and molecular weights. The paper is allowed to remain in the solvent until the uppermost pigment band nears the top of the paper. This photograph shows the four main pigments separated from green plants using paper chromatography.

The primary pigments in green plants are chlorophylls, represented by chlorophyll a and b, which appear green.