Paper chromatography separates plant pigments based on their varying solubilities in a solvent.
The Process Explained
Here's a detailed breakdown of how paper chromatography works to separate plant pigments:
- Preparation: A small amount of plant extract, containing various pigments, is spotted near the bottom of a piece of chromatography paper.
- Solvent Action: The bottom edge of the paper is then placed into a suitable solvent, such as a mixture of petroleum ether, acetone and a small percentage of water in a container, ensuring the spot of extract is above the solvent level.
- Pigment Separation: As the solvent moves up the paper by capillary action, it carries the dissolved pigments with it. The solvent carries the dissolved pigments as it moves up the paper. The rate at which each pigment moves is determined by its solubility in the solvent and its interaction with the paper itself.
- Differential Movement: Pigments that are highly soluble in the solvent will travel further up the paper, while those that are less soluble will move a shorter distance. A pigment that is the most soluble will travel the greatest distance and a pigment that is less soluble will move a shorter distance.
- Visualization: Once the solvent has moved a suitable distance, the paper is removed and dried. The different pigments will be visible as distinct, separated spots along the paper.
Factors Affecting Separation
| Factor | Impact |
|---|---|
| Pigment Solubility | Pigments with higher solubility in the solvent will move further, leading to greater separation. |
| Solvent Choice | The solvent's composition significantly influences the separation. Different solvents have varying affinities for different pigments. |
| Paper Interaction | Some pigments may interact with the paper, slowing their movement and leading to further separation. |
Example
Imagine separating green chlorophyll, yellow xanthophyll, and orange carotene. Carotene, being the most soluble in a particular solvent, might be found at the top of the chromatogram, with xanthophyll below it, and finally, the chlorophyll at the bottom due to lower solubility.
In summary, paper chromatography separates plant pigments based on their differing solubilities, with the solvent acting as the carrier and the paper acting as the stationary phase. This allows for a clear visual representation of the pigments present in a plant extract.
