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Paper chromatography.

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Biology Lab report Title : Paper chromatography Aim : to separate and identify of the pigments in leaves by paper chromatography Principle of design: In this experiment, a strip of filter paper containing a small spot of concentrated chlorophyll pigment is dipped in a mixture of developing solvent, the pigments was carried up the strip as the solvents move up. Since the solvents moved at different rates and pigments had different solubilities in them, the pigments gradually become separated. When the solvent was near the top of the paper, the paper was removed. After that, Rf (Relative front) for that substance were calculated. In this experiment, Rf values were used to identify the different substances present in the leaf extract mixture. Instructions: 1. 3 leaves of spinach were ground in pestle and mortar by 2 cm3 of extraction solvent 2. the developing solvent was added into the boiling tube and it just touched the lower edge of the paper strip. ...read more.


8. The chromatogram was allowed to develop until the solvent front is 2 cm from the upper edge of paper strip. 9. The paper strip was taken out and a light pencil line was ruled to mark the solvent front. 10. The pigment patches were circled immediately with a pencil. 11. The Rf values for the different pigments in the leaf extract were calculated. Results: The distance that the solvent travels = 9.3cm Rf of the top yellow spot = 8.9/ 9.3 = 0.96cm Rf of the middle orange spot = 6.8/ 9.3 = 0.73cm Rf of the bottom bright green spot = 5.7/9.3 = 0.61cm Rf of the lowest green spot = 4.4/9.3 = 0.47cm Therefore the top yellow spot is carotene pigment, the middle orange spot is xanthophyll pigment, the bottom bright green spot is chlorophyll a pigment, and the lowest green spot is chlorophyll b pigment. ...read more.


The pigment with the greatest adsorption ability traveled up the shortest distance, and the pigment with the weakest adsorption ability traveled up the longest distance. In this experiment, carotene had the weakest adsorption ability, and chlorophyll b had the greatest adsorption ability. The strip of filter paper should be freely suspended in the test tube, this is because the movement of the pigment on the paper in contact or near the glass would cause the particles to be attracted to the side such that net charge of the force would be towards the side. The test tube must be stoppered. This is to produce a saturated atmosphere in the test tube. Also, it was to prevent the evaporation of the solvent, which is toxic. Conclusion: There were four pigments being separated from chlorophyll, they were chlorophyll b, which is the least soluble, heaviest and have the greatest ability of adsorption, chlorophyll a, xanthophyll II and carotene, which is the most soluble, lightest and have the weakest ability of adsorption. ...read more.

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