1. Chromatography
Aspirin lab

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

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

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

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

6. 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

7. Chromatography images
Chlorophyll Aspirin

8. 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

9. 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

10. Approximate the Rf values of the pigments below

11. Other forms of Chromatography
Column chromatography

12. HPLC- High Pressure Liquid Chromatography