Chromatography is a technique used to separate or purify mixtures.
Column chromatography involves a liquid mobile phase and a solid stationary phase.
Components normally interact with the mobile phase and stationary phase via intermolecular interactions.
Task: See if you can name the intermolecular interactions and put them in order of strength.
The rate at which each component moves down the column is determined by its relative affinity for the mobile phase and stationary phase.
In normal phase column chromatography, the stationary phase is polar and the mobile phase is non-polar. therefore _______ components interact more strongly with the stationary phase and move through the column ______.
In reverse phase column chromatography, the stationary phase is non-polar and the mobile phase is polar. . therefore _______ components interact more strongly with the stationary phase and move through the column ______.
_______ phase chromatography _______ phase chromatography
Silica (SiO2) is a common stationary phase. You can find silica in sand on the beach. But the silica in columns is a bit different. It has lots of holes in it, called pores. The surface of all those holes is covered in Si-OH groups. We call these silanol groups. The holes give the silica a really high surface area. This means lots of space for polar molecules to stick to!
The tactile model
The tactile model can be used to illustrate the way in which column chromatography works. The plastic and wool felt balls represent the components in the mixture and the Velcro inside the column represents the stationary phase.
Task: Pour the balls down the column and feel which balls come out.
Question 1: Why did the balls separate in the column
Question 2: Relate this back to standard chromatography