नमस्कार मित्रांनो इयत्ता बारावी Biology या Subject च्या Practical मध्ये PART - B: Demonstration Experiments (Spotting) हा भाग Practical Exam च्या दृष्टीने फार महत्त्वाचा आहे. या Blog Post मध्ये आपण Spotting Practical Number 2: Separation of plant (photosynthetic) pigments by paper chromatography ह्या Practical Experiment चे Answer पाहणार आहोत. खाली दिलेल्या उत्तरांमध्ये काही अडचण असल्यास आम्हाला comment करा किंवा तुमच्या संबंधीत विषय शिक्षकांशी चर्चा करा.
B. DEMONSTRATION EXPERIMENTS (Spotting)
2. Separation of plant (photosynthetic) pigments by paper chromatography.
Aim :- Separation of plant (photosynthetic) pigments by paper chromatography.
The plants show presence of many pigments. The different photosynthetic pigments resent in the leaf cells are: chlorophylls, carotenes and xanthophylls.
These photosynthetic pigments can be separated using the technique of paper chromatography.
Principle :- The separation of solutes (chloroplast pigments) is based on the liquid-liquid partitioning of pigments in paper chromatography. The partitioning takes place between the solvent (water) molecules (static phase) adsorbed to the cellulosic matter of the paper (capillary action) and organic (mobile) phase.
Requirements :- Chromatography chamber, chromatography paper (Whatman's filter paper no.1), pestle-mortar, capillary tube, muslin cloth and suitable solvent system, fresh spinach caves, etc.
Figure :-
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| Fig. Separation of chloroplast pigments by paper chromatography |
Procedure :-
• Prepare solvent system - Petroleum ether: acetone (90:10), and pour it in the chromatography chamber and cover it tightly. Keep it undisturbed for 1 hour for saturation of the solvent system.
• Take a few spinach leaves (5 gms), wash and keep them dry.
• Grind these leaves in acetone (organic solvent) with a small amount of MgCl,. (as a buffer)
• Filter it through muslin cloth and collect the filtrate.
• Cut a suitable strip of chromatographic paper and mark the loading point with a pencil. With the help of a capillary tube, the extract or filtrate is repeatedly loaded at the loading point.
• Allow it to dry.
• Now place the strip in the solvent system in such a way that its lower tip gets dipped in the solvent.
• Take care not to dip it too close to the loaded spot. Cover the chamber and keep it undisturbed to get the chromatogram run.
• Let the solvent travel close to the other end of the chromatography paper. Different pigment carried along with the solvent up to different heights on the basis of their molecular weight
• Take out the paper, allow it to dry and observe the separation of photosynthetic pigments in the form of separate bands of different colours.
Caution : Perform the experiment in a well ventilated laboratory.
Observation :- On the strip we can observe the separation of photosynthetic pigments as bands of different colours in a particular sequence. From the loaded spot up to the top the sequence is; chlorophyll (yellowish green), chlorophyll-a (bluish green), xanthophylls (yellow) and carotene (orange).
Questions
1. What is the composition of solvent used for separation of photosynthetic pigments?
Ans :- The Solvent used for the separation of photosynthetic pigments is Petroleum ether and acetone in the proportion 9:1.
2. Which pigment reaches to the top of the chromatography paper?
Ans :- Carotene reaches the top of the chromatography paper
3. Which photosynthetic pigment is bluish green in colour?
Ans :- The bluish-green photosynthetic pigment is chlorophyll-a.
4. Why acetone and MgCl2 are used while grinding the leaves?
Ans :- Acetone acts as an organic solvent while MgCl2 acts as a buffer.
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