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Chromatography Aspirin lab
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Definition Physical method to analyze/separate substances of a homogeneous mixture
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Components of a Chromatography System
Solid phase: Chromatography paper or cellulose/silica covered glass plates Thin Layer Chromatography (TLC) Do not touch coating!
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Components of a Chromatography System
Liquid phase: H2O, ether, acetone, ethanol, alone or as mixtures Aspirin lab: ethyl acetate
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Chromatography Principle
Substances have different chemical properties and vary in their: Solubility in the Liquid Phase Absorption to the Solid Phase
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TLC-Procedure Start: Draw pencil line approximately 1 cm from bottom edge of paper Place substances on start line a/b ½ cm apart Fill chamber with ½ cm of solution Place TLC plate in chamber Solvent migrates up solid phase (capillary action) carrying substances along Stop: When solvent front is approximately 1 cm from top edge, take out and mark with pencil Circle separated substances with pencil under UV light
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Chromatography images
Chlorophyll Aspirin
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Calculating Reference values: Rf
Measure distance Solvent Front (SF) has migrated from start in mm Measure distance each spot (a,b,c) has migrated from start in mm Divide: a/SF ; b/SF ; c/SF The value must always be between 0 -1
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Rf values are A. Specific
To type of solvent and solid phase Will change if liquid or solid phase are changed B. Non-specific To the migration length/time within the same system chromatography video
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Approximate the Rf values of the pigments below
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Other forms of Chromatography
Column chromatography
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HPLC- High Pressure Liquid Chromatography
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