plant_procedures - Separation and Identification of Plant...

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1 Separation and Identification of Plant Pigments Dr. Gergens - SD Mesa College PURPOSE In this experiment, the photosynthetic pigments common to all flowering plants will be extracted by liquid- liquid extraction. The four main pigment components of plant leaves are chlorophyll a, chlorophyll b, carotene, and xanthophyll. The solvents needed for the extraction and separation will be petroleum ether, diethyl ether, methanol, and water. Finally, these pigments will be analyzed by measuring the absorption spectra of the plant pigments. BACKGROUND The four main pigment components of plant leaves are chlorophyll a, chlorophyll b, carotene, and xanthophyll. While most plant leaves appear green to our eyes, several different photosynthetic pigments of various colors are usually present in the chloroplast of green plants. The colors of these pigments are due to the numerous double bonds in their structure. The green color of leaves is provided by chlorophyll a and b, which absorb most of the light energy needed for photosynthesis to occur. The greatest absorption of light by chlorophyll is in the red, blue and violet wavelengths. Associated with these green pigments are several other pigments known as carotenoids. These are commonly yellow to red in color, and are also involved in harvesting light energy for photosynthesis. SAFETY PRECAUTIONS Wear safety goggles and aprons at all times in the laboratory. No open flames in or outside the door of the laboratory. The solvents in this experiment are highly flammable. Diethyl ether is very volatile and is highly flammable. Petroleum ether and methanol are flammable as well. Work underneath the hood. Keep all Erlenmeyer flasks, beakers, and solvent containers capped and/or covered. 30% methanolic KOH is extremely corrosive. Avoid contact with skin, eye, or cloths. If you spill any on yourself, rinse thoroughly with water and contact the instructor. Dispose of all reagents in the reclaim container provide in the fume hood. The chlorophyll solution is very concentrated. It will stain skin, cloths, etc. Clean up any spill. Wash all glassware to avoid any permanent green stains. Keep in mind the safety precautions when using a separatory funnel: a. never extract hot solutions. b. never forget to vent constantly. c. never clamp a separatory funnel to a ring stand; use an iron ring. d. never forget to unplug the glass stopper when draining.
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2 EXPERIMENTAL PROCEDURE PART A. Separation of Photosynthetic Pigments by Liquid-Liquid Extraction. Take care not to spill this solution. Concentrated chlorophyll solutions will produce a very nasty green stain on anything it comes in contact with. Please was all glassware with soap as soon as possible to avoid permanent green strains. 0.
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This note was uploaded on 09/09/2011 for the course CHEM 231l taught by Professor Gergens during the Spring '11 term at Mesa CC.

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plant_procedures - Separation and Identification of Plant...

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