1. Chromatography Chromo: color Graph: to write
In the mid 1900s used to separate and analyze naturally occurring pigments like those in leaves.
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2. Real life uses for Chromatography
Law Enforcement – to compare a sample found at a crime scene to samples from suspects
Environmental Agency – determine the kinds of pollutants and level of pollutants
Pharmaceutical Company – determine amount of each chemical found in new product
Hospital – detect levels of chemicals in a patient’s blood stream
Manufacturing Plant – to purify a chemical needed to make a product

3. Solvent front
Plate: stationary phase
Pigments in the mixture
Solvent: mobile phase

4. Definition of Chromatography
Chromatography separates components of a mixture by their distinctive attraction to the mobile phase and the stationary phase.
The mixture looks homogenous before procedure but is made of more than one component
Separates: spreads out for analysis or to make a pure sample
Two phases -- one moves and one stays still

5. Phases Compound is placed on a stationary phase
Made of paper, beads, solid
On Monday made of silica gel plate
Mobile phase passes through the stationary phase
Liquid or gas
On Monday made of solvent 50% acetone/ H2O
Some compounds in mixture spend more time in mobile phase than others and therefore move faster/ farther
What determines how long the pigment spends in the mobile phase?

6. Polarity
Within covalent molecules, atoms share electrons If the atoms share equally the molecule is non-polar Typical of molecules made up of carbon and hydrogen If the atoms do not share electrons equally, then portions of the molecule are charged. These molecules are called polar.

7. Polarity and Solubility
In general: Like dissolves like
More polar substances dissolve best in polar solvents.
Less polar substances dissolve best in non-polar solvents.

8. Solvent front
Plate: stationary phase
Pigments in the mixture
Solvent: mobile phase

9. Molecular View of Chromatography
Stationary phase – molecules are here when they are not dissolved
Mobile phase – molecules are here when they are dissolved
Blue molecules spends the most time in mobile phase because they are the most polar. Red molecules spends the most time in stationary phase because they are the least polar.

10. D2 = distance to solvent
front
Rf is not calculated with distance between pigments or distance
between pigments and solvent front.
D1 = distance to pigment
Rf = D1/D2
= 6.2cm/12.4cm
= 0.5
Rf = retention factor
= ratio of distance travelled

11. Illustration of Chromatography
Stationary Phase
Separation
Mobile Phase
Mixture
Components
Components
Affinity to Stationary Phase
Affinity to Mobile Phase
Blue
Insoluble in Mobile Phase
Black
     
 
Red
    
Yellow 
        

12. Optimizing information
Careful choice of solvent and stationary phase.
Separation visible at 50%-70%
View under UV and ambient light to see all pigments. 0%
20%
50%
70%
100%
Concentration of Isopropanol

13. To make your lab work… Mark plate in pencil Don’t chip plate
Avoid getting hand oil on plate
Spot pigments above level of solvent

14. Types of Chromatography
Paper Chromatography – separates dried liquid samples with a liquid solvent (mobile phase) and a paper strip (stationary phase)
Thin-Layer Chromatography – separates dried liquid samples with a liquid solvent (mobile phase) and a glass plate covered with a thin layer of alumina or silica gel (stationary phase)
Liquid Chromatography – separates liquid samples with a liquid solvent (mobile phase) and a column composed of solid beads (stationary phase)
Gas Chromatography – separates vaporized samples with a carrier gas (mobile phase) and a column composed of a liquid or of solid beads (stationary phase)