Experiment Three: Separation and Identification of Food Dyes by Paper Chromatography
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Useful for separating mixtures of gases or components that can be vaporized without thermally decomposing
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Gas-liquid Chromatography
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Useful for separating components that would decompose if they were vaporized, such as carbohydrates and biological molecules
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High-performance Liquid Chromatography
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Composed of silica gel, alumina or cellulose stabilized on a glass plate
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Thin Layer Chromatography
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A mixture dissolved into a gas or liquid
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What is the mobile phase?
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The mobile phase moves over a solid components
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What is a stationary phase? •
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Species being analyzed, have to separate these species before analysis
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Samples contain multiple analytes, what does that mean?
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does not involve chemical nature of the species that are to be separated, based on phys characteristics (sorting candy, based on color; how to do this for solubility)
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What is Physical separation
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what we are going to do in the lab, separate and identify the species in a mixture, chromatography
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What is Chemical separation
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to resolve(separate) the components of a mixture, chemical compounds tend to partition (arrange and separate) based on polarity, capillary action
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What is Chromatography
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the preferential attraction of the components of a mixture for either a stationary or mobile phase. Affinity is based on attractive forces that exist between particles (molecs, atoms, ions), and the mobile and stationary phases. Differences in affinity for components of a mixture will result in separation
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What is the Separation based on?
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Component "A" will flow readily with mobile phase than "B" (it has an affinity for the mobile phase), A will travel farther
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If a mixture is composed of "A" and "B"..."A" has a strong affinity for the mobile phase, but a weak affinity for the stationary phase; B has the opposite, what will happen?
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(Rf = Distance traveled by "A" / Distance traveled by solvent), out of 1
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What is the Retention Factor
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• Close to 0=stationary • Far from 0= mobile
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What does it mean if the Retention Factor is close or far from 0?
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Filter paper = stationary phase, several different mobile phases. Select mobile phase for which the dyes have the greatest difference in affinity. This will maximize the difference in retention factors and yield the most complete separation
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What are the different stationary phases and mobile phases? What mobile phase do you choose? Why?
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First we extracted dye mixtures from assorted candy, by swirling it in acetic acid, then we added 5% ammonia to make the dye solution basic. Made 4 salt solutions (.1% salt, deionized water, ½ deionized, ½ ethanol; more ethanol than deionized water). Then we made 4 chromatography papers and labeled them with different dyes, then measured retention factors; saw which solution was the best, and then had a small drop of unknown, found out what was in there. Also analyze the color in the candy
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Point of the Lab?
