Lab Report for Chromatography

Study Questions:

One of the requirements for the photosynthesis process to occur, the plant cells need sufficient light. Pigments are the substances that absorbed visible light. Different pigments absorb light of different wavelengths.

From the absorption spectrum of chlorophyll a, it suggests that blue and red light work best for photosynthesis.

There is a high degree correlation between the absorption spectra of leaf and the absorption spectra of chlorophyll a, chlorophyll b and carotene. It is because those pigments are used to absorb the visible light for the leaf.

The phenomenon of capillarity is involved in this technique. The relative molecular mass of chlorophyll b is greater than chlorophyll a. Since it is lighter, chlorophyll b can cause more rise of the chromatography solvent in the microscopic spaces between the fibres of the chromatographic strip. So, this technique is very sensitive laboratory tool since it can differentiate existence pigments in a plant based on the molecular structure of the pigments.

From the experiment results, the Carotenoid has the lightest molecular weight.

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Its ratio of front is less than chlorophyll b, meaning that it can cause more raise between the microscopic spaces between the fibres of chromatographic strip. There is correlation between molecular weight and the manner in which the pigments separate. As the molecular weight decrease, the respective coloured band for each pigment can rise higher.

Two physical phenomena that make paper chromatography possible are the capillarity and the solubility

The other uses for paper chromatography are separating amino acids and sugar.

Limitations

Since this is a qualitative experiment, there are a lot of precaution steps that must be taken during the experiment. Firstly, this experiment needs a chromatography paper strips. During the handling of the strips, it must be only touched on the edges and near one end only to avoid any errors occur during the phenomena of capillarity.

Then, a capillary tube is used to spot the pigment on the paper strip. It must be ensured that only a small spot must be spotted on the strip. It must be neatly respotted until a dark green spot is produced to get more reliable result. Another step is during the placement of the strip in the tube. It must be ensured that the pigments extract spot is not immersed in the solvent.

The main problem during the experiment is the lack of time to do the experiment carefully since it must be completed in 2 period times. So, more time should be provided to finish this experiment. For example, during the respotted period of the pigments spot, it must be ensure that each spot is dry before another spot is produced.

Conclusion:

Chromatography is a technique to differentiate several pigments in plant. The photosynthetic pigments in spinach are chlorophyll b and Carotenoid. However, theoretically, it should have 4 pigments, chlorophyll a, chlorophyll b, xanthophyll, and carotene. During the chromatography process, a solvent mixture that causes the individual pigments to be separated during the run is selected; the loaded chromatogram is lowered into the solvent and the solvent travels up the paper; the run is stopped when the solvent front nears the top of the paper.