Types of Chromatography

Adsorption, partition, ion-exchange, size-exclusion, affinity

Stationary phase: solid

Mobile phase: liquid or gas

• Solute is absorbed onto the surface of solid particles

• The more strongly a solute is absorbed, the slower it travels through the column

• Example: Thin layer chromatography

Adsorption Chromatography

Stationary phase: liquid bonded to a solid support

Mobile phase: liquid or gas

Solute partitions between the stationary liquid and the mobile phase

Example: Gas chromatography

Stationary phase: liquid polymer is is bonded to the inside surface of an open tube of fused silica

Mobile phase: flowing gas

Partition Chromatography

Stationary phase: anions or cations covalently attached to the stationary phase, using a RESIN

Mobile phase: liquid containing eluent ions

Solute ions of the opposite charge are attracted to the stationary phase

Ion-exchange Chromatography

Stationary phase: porous gel

Mobile phase: liquid or gas

This technique separates molecules by size, with larger solutes passing through most quickly

The pores are small enough to exclude large solute molecules but not small ones

Small molecules take longer to pass through the column because they enter the gel and are shattered from the mobile phase flowing around the gel

Based on physical size of molecules not interactions between the phases

Size-exclusion Chromatography

Stationary phase: a covalently bonded molecule that uses molecular recognition to bind with incredibly high specificity to the analyte

Mobile phase: liquid

How is the analyte eluted?

After other solutes have been washed from the column, the desired analyte is dislodged by changing the pH or ionic strength

Affinity chromatography

The speed of the mobile phase passing through the column is expressed as a volume flow