OBJECTIVES: The objective of this experiment was to extract plant leaf pigments and determining them by using the Rf values obtained from the paper chromatography technique. The hypothesis of the experiment was that all of the five listed pigments would be present in the extracted plant leaf according to the Rf values.
PROCEDURE/APPARATUS: The equipments used were a 18 x 150 mm test tube with stopper, graduated cylinders, Erlenmeyer flask, mortar and pestle, metric ruler, tall jar, acetone, tiny test tube, small brown bottle, petroleum ether, plant leaf, dried parsley flakes, water, glass petri dish, stapler, sand, spatula, pipette, capillary tube, Whatman filter paper, a 50 ml chromatography solvent, and goggles (to be worn at all times). The steps to performing the experiment were:
1. Pour 50 ml of chromatography solvent into the tall jar and cover it with half of the petri dish.
2. Take ½ teaspoon of dried parsley flakes and ¼ teaspoon of sand in the mortar. Tear a plant leaf into small pieces, and place it in the mortar along with the other materials and grind it for 10 seconds. After that, place the ground materials in the test tube and add 5 ml of acetone.
3. Shake for 10 seconds, and after 10 minutes add 5 ml of water. Then, add 3 ml of petroleum ether and shake for 5 seconds. The pigment will eventually be found on the upper layer; remove it with a pipette and place it in a small test tube in the brown bottle. Note: dispose of the remaining materials.
4. Draw a faint pencil line on a filter paper, 1.5 cm from one edge. Then, using a capillary tube, make 6 or 7 dots on the pencil line (repeat the step till the dots are dark enough).
5. Form the paper into a cylinder, staple it and place it in the jar. Make it stand for 30-40 minutes. Afterwards, take the paper out and immediately put a pencil mark at the top of the solvent front. Then compute the Rf values using the distance the pigment traveled in cm/ the distance the solvent traveled in cm. Record each value and compare the pigment.
DATA: The table shows the Rf values for the plant leaf pigments.
PIGMENT Rf (GIVEN VALUES) Rf (LAB VALUES)
Carotene 1 (golden yellow) .96 .87
Chlorophyll a (green) .39 .33
Chlorophyll b (yellow green) .26 .19
Petunidin (gray-violet) .68 .59
Carotene 2 (yellow) .52 .46
CONCLUSION: From this experiment, it was concluded that plant leaf pigments were extracted by using chromatography, which is a technique to discover chemical components. The Rf values for the plant leaf pigments that were already given, differed from the calculated lab values (weren’t exactly the same as the given values), but in general, all five of the pigments were present in the plant leaf. All the data were recorded or shown in the chromatogram, a pattern formed by substances that have been separated by chromatography. The result is the chromatogram showing all five of the colored pigments in different places, in relation to the distance the solvent traveled.