Chromatography Aspirin lab

Definition Physical method to analyze/separate substances of a homogeneous mixture

Components of a Chromatography System Solid phase: Chromatography paper or cellulose/silica covered glass plates Thin Layer Chromatography (TLC) Do not touch coating!

Components of a Chromatography System Liquid phase: H2O, ether, acetone, ethanol, alone or as mixtures Aspirin lab: ethyl acetate

Chromatography Principle Substances have different chemical properties and vary in their: Solubility in the Liquid Phase Absorption to the Solid Phase

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

Chromatography images Chlorophyll Aspirin

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

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

Approximate the Rf values of the pigments below

Other forms of Chromatography Column chromatography

HPLC- High Pressure Liquid Chromatography