Chromatography

Question 1

What is gas-liquid chromatography used for?

Answer 1

• Gas-liquid chromatography is used to seperate mixtures of volatile liquids (ones that turn into gases easily).

Question 2

What is chromatography used for, and what are the two phases?

Answer 2

• Chromatograhpy is used for separating stuff in a mixture.
• It has two phases:

Mobile phase: where the molecules can move. This is always a liquid or gas.

Stationary phase: where the molecules can’t move; this must be a solid, or a liquid held in a solid.

• The components in a mixture separate out as the mobile phase moves through the stationary phase.

Question 3

Outline column chromtography.

Answer 3

Mostly used for purifying an organic product.

1. Glass column packed with a slurry of an absorbent material; aluminium oxide (Al₂O₃), coated with water.
   * *Stationary phase.**
2. Mixture to be separated is added to the top of the colmn and allowed to drain down into the slurry.
3. A solvent is then run slowly and continually through the column. Mobile phase.
4. As the mixture is washed through the column, its components are separated out according to how soluble they are in the mobile phase and how strongly they are adsrobed onto the stationary phase (retention).
5. Each different component will spend some time adsorbed onto the stationary phase and some time dissolved in the mobile phase. The more soluble each component is in the mobile phase, the quicker it’ll pass through the column.

Separation by column chromatography depends on the balance between solubility in the moving phase and retention in the stationary phase.