The black ink is actually a mixture of several different pigments, or coloring agents.
Some pigments dissolve in water easier and are pulled with the water farther up the paper.
Others are more attracted to the paper and move more slowly.
Usually smaller molecules will move farther than larger ones.
Why do different pigments travel different distances?
The solvent carries the dissolved pigments as it moves up the paper. The pigments are carried at different rates because they are not equally soluble. A pigment that is the most soluble will travel the greatest distance and a pigment that is less soluble will move a shorter distance.
Why do different colors travel different distances in paper chromatography?
In paper chromatography different pigments can be separated based on their solubility, or their ability to dissolve in water. The more soluble a pigment is, the more readily it will dissolve in the mobile phase and the farther it will usually travel as it is carried by the water being absorbed into the paper.
What determines how far a pigment will travel in chromatography?
The speed at which a particular pigment moves depends on its relative affinities for the two solvent phases; if it has no affinity whatever for the water phase, it will travel at maximum speed, just behind the solvent-front (eg beta-carotene); on the other hand, if the pigment has no affinity whatever for the non-polar
Why does chlorophyll a travel further?
One can then state that the reason why carotene moved the furthest is because of how soluble it is to the acetone solvent. On the other hand, one can say that chlorophyll b traveled such a small distance from the pigment extract origin because of its tendency to stick to the paper’s fibers.
Why does Xanthophyll travel the farthest?
Xanthophyll contains oxygen and does not travel quite as far with the solvent because it is less soluble the beta carotene and forms hydrogen bonds with the paper. Chlorophylls are bound more tightly to the paper than the other two, so they travel the shortest distance.
What are the RF values of pigments?
You can obtain Rf values for each of your pigment lines using the equation in Figure 1. The literature reports the following Rf values for each component: Rf = 0.16 for xanthophyll, Rf = 0.32 for chlorophyll b, Rf = 0.44 for chlorophyll a, and Rf = 0.95 for β- carotene.
Why can’t the chromatography paper touch the sides of the beaker?
It is important that the filter paper did not touch the walls of the test tube because if touching the side walls, water would absorb from the sides as well as the bottom of the filter paper.
Why do some inks travel further in chromatography?
It is often used when the dissolved substances are coloured, such as inks, food colourings and plant dyes. It works because some of the coloured substances dissolve in the solvent used better than others, so they travel further up the paper.
How can you identify an unknown color pigment?
It is used in the sequencing of DNA and RNA. Paper chromatography is used as a qualitative analytical chemistry technique for identifying and separating colored mixtures like pigments. It is used in scientific studies to identify unknown organic and inorganic compounds from a mixture.