P19 CROMATOGRAPHY

OBJECTIVES

• To know the bases of chromatographic analysis.
• To learn the procedure for separating the photosynthetic pigments. 

MATERIAL 

• ethanol
• Funnel
• paper 
• spatula
• Cromatography paper
• mortar
• Petri dish
• spinach 
• Calcium carbonate

PROCEDURE

• Wash the spinach and cut them, then dry them.
• Grind the spinach in a mortar and add 50 ml of ethanol and a small amount of calcium carbonate, which fits at the tip of the spatula.
• Filter the mixture into a funnel with filter paper.
• Put a part of the mixture in a Petri dish (3-4 mm high).
• Put a rectangle of paper for chromatography in form V, and wait for the pigments to be differentiated.

RESULTS

The different pigments that are from bottom to top are:

Beta carotene (red - orange)

Chlorophyll alpha (bluish green)

Chlorophyll beta (bright light green)

Xanthophylls (yellow)

QUESTIONS

Why do we add calcium carbonate?

To avoid the degradation of the pigments.

Which is the colour of every pigment

• Beta carotene (red - orange)
• Chlorophyll alpha (bluish green)
•  Chlorophyll beta (bright light green
• Xanthophylls (yellow)

For what purpose it does have different colour pigments?

To know the different solubility of photosynthetic pigments in an organic solvent such as ethanol, which is miscible with water.

Why do they separate in the paper? 

When the alcohol is placed with the pigments dissolved by a chromatography paper, the different pigments are separated as the medium is increasingly poorer in ethanol and richer in water.