Exp 6 - Analytical Chemistry 241 Lab

Exp 6 - Analytical Chemistry 241 Lab - Experiment 6: The...

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Experiment 6: The Extraction of Plant Pigments fro Spinach and the Subsequent Separation and Analysis of the Extracted Pigments Using Liquid Chromatography Flora Vo Lab Partner: Taylor Scott 2 April 2007 TA: BJ Privett Chem 241L: Section 410, Room 401 Thursday 1 PM – 4 PM Pledge: I pledge that no unauthorized assistance has been given or received in the completion of the work presented in this report. ________________________________
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Introduction Using reverse-phase liquid chromatography and spectrophotometric detection, the extracted pigments from spinach will be separated and analyzed. Students will learn about plant pigments, how to extract pigments from plant cells, to use liquid chromatography to separate complex mixtures, and to determine efficiency using selectivity and resolution. There are three families of plain pigments: porphyrins, carotenoids, and flavenoids. The porphyrins consist of the chlorophylls a and b. These pigments are usually in green plants and are involved in photosynthesis. However, when sunlight decreases, the production of chlorophyll decreases also. As a result, leaves change colors in the fall. The predominant pigments in fall leaves are carotenoids. This family has two subgroups: carotenes (orange- yellow and red pigments) and xanthophylls (yellow). Like the porphyrins, this family is also involved in photosynthesis to a smaller degree. However, the amount of carotenoids in plant cells remains fairly constant year round. The last family is the flavonoids, which have three classes: flavones, flavonol, and anthocyanin. Most flavonoids contribute to the pigments in flowering plants, although there are some flavonoids in leaves. Anthocyanin, which reflects red, blue, and purple colors, has a glucose group, and its production is dependent on carbohydrate availability, sunlight, and temperature. Also, it has the ability to change color according to the pH. Anthocyanin is red in the most acidic conditions, and as the medium gets more basic, it turns to purple and then blue. It is also responsible for leaf coloration in the fall. There are several ways to extract pigments from plant cells. A mortar and pestle, along with sand, can be used. Also, a blender and acetone can be used to break up the plant cells, and this becomes an organic solution. Then, the same volume of saturated salt solution would be added to the organic solution, creating two layers. The aqueous layer will contain most of the
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flavonoids and Xanthophylls (trihydroxy derivatives.) the organic layer will contain most of the chlorophylls, carotenes, and xanthophylls (mono- and dihydroxy derivitives.) The sodium molecules are attracted to the water, and this attraction allows most of the pigments to be salted into the polar layer. In the non-aqueous layer, the carotenes are the least polar, chlorophyll is at an intermediate level, and the xanthophylls are the most polar. When the pigments are extracted, it can be analyzed with chromatography.
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Exp 6 - Analytical Chemistry 241 Lab - Experiment 6: The...

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