3.16 Chromatography

A state such as solid, liquid, gas

The phase that moves

The phase that doesn’t move

The balance between solubility in the moving phase and retention in the stationary phase

By adsorption

By solubility

Polarity

Thin layer of SiO₂ or Al₂O₃ on an inert support

Prevents evaporation and creates a saturated environment

Ninhydrin UV light Iodine

Ammino acids

Distance moved by spot / Distance moved by the solvent

• Similar compounds will have similar Rf values • Unknown compounds have no reference values • Difficult to find a solvent that gives good separation

• Checking purity of compounds • Identifying components in a mixture

Separating and collecting larger amounts of materials

Column packed with solid SiO₂ or Al₂O₃

Very sensitive quantitative method

Separating volatile compounds

• Solid inside column • Thin layer of liquid on a solid support inside the column

Inert carrier gas (He or N₂) which move through the column

• Sample is injected into chromatograph where it vapourises • Inert carrier gas flushes mixture through the column • Components slow down when interacting with the stationary phase • Each leaves with a different retention time

Time taken for a component to pass from the column inlet to the detector

Minimum number of components in the mixture (A larger peak may hide a smaller peak)

Proportional to the amount of that component in the mixture