1) The experiment aims to extract photosynthetic pigments like chlorophyll from different plant parts and identify them by their absorption wavelengths. 2) Chlorophyll a absorbs maximally at 430nm and chlorophyll b at 625nm. Plant samples are ground in acetone or ethanol and their absorbances measured. 3) Absorption values will be highest in leaves, indicating they contain the most chlorophyll for harvesting solar energy through photosynthesis.

1. SHREE MALLIKARJUN COLLEGE CLASS:SYBSC
SAFETY: Refer to MSDS of acetone and ethanol
-Dr. Mithil S. FalDesai
Aim: Extraction of photosynthetic pigments from different parts of the plants and its identification from
absorption wavelength.
Chemicals: acetone or ethanol
Apparatus/Instrument: Standard volumetric flask, beakers, funnel, measuring cylinder, dropper, mortar
and pestle, and colorimeter
Theory: The photosynthetic pigment chlorophyll is responsible for harvesting solar energy naturally. It is a
green colour compound. Usually two types of green pigments are present in plant chlorophyll a and
chlorophyll b which show maximum absorption at 430 and 625 nm, respectively. The absorption of these
pigments can be studied using a colorimeter.
Procedure: 1) Wash the sample plant thoroughly and allow it to dry for 10-15 min at room temperature.
2) Make small pieces of different part of the plants (leaves/stem/roots) and weigh about 5 g each
separately.
3) Grind the different parts of plant separately in 10 mL of acetone/ethanol.
(Calibrate the colorimeter using acetone/ethanol)
4) Filter the solution and measure its absorbance at different wavelength.
5) Compare the wavelength of the light which is absorbed maximum.
Observation:
Table 1.
Filter 430 nm 470 nm 525 nm 568 nm 601 nm 625 nm 660 nm
Leaves
Stem
Roots
Results: i) Maximum absorption for chlorophyll is shown at ____nm.
ii) In given plant sample amount of chlorophyll is higher in leaves/stem/roots compared to other parts of
plant.
Further reading
1) Experiments in Applied Chemistry, S. Rattan, S. K Kataria, and Sons.
2) O. P. Virmani and A.K. Narula, Applied Chemistry theory and Practice, New Age, International
Publishers, IInd Edition.
3. Robert Bruce Thompson, Illustrated Guide to Home Chemistry Experiments O’Reilly Media. Inc.
Questions.
1) Extract of leaves shows two absorption maxima at 430 and 625 nm. Why?
2) Which is the metal ion present in the chlorophyll?
3) What is the function of chlorophyll?
4) Why some leaves are red in colour?