Column Chromatography and Gas-Liquid Chromatography
This section covers the column chromatography setup instructions and principles of gas-liquid chromatography GLC, two powerful separation techniques used in analytical chemistry.
Column Chromatography:
• Uses a long vertical glass tube or burette as the column
• Stationary phase: inert solid e.g.,powderedsilicageloralumina
• Mobile phase: liquid solvent
Column chromatography procedure:
- Carefully pack the column with the stationary phase
- Saturate the column with solvent
- Dissolve the sample mixture in solvent and add to the top of the column
- Add more solvent eluent to the column
- Allow gravity to pull the mobile phase through, or use pressure to speed up the process
- Collect separated components as they exit the column
Highlight: Proper column setup is crucial - cracks in the stationary phase can lead to separation issues.
Gas-Liquid Chromatography GLC:
• Used for gases, volatile liquids, and solids in vapor form
• Stationary phase: non-volatile liquid on a solid support
• Mobile phase: inert carrier gas e.g.,heliumornitrogen
Gas-liquid chromatography principle:
- Inject the sample through a self-sealing disc
- Vaporize the sample
- Carrier gas moves sample molecules through the stationary phase
- Detector records retention times of separated components
- Chromatogram shows peaks representing each volatile compound
Vocabulary: Retention time - the time taken for a component to travel through the column
Definition: In GLC, retention time is used instead of Rf values to identify and quantify components.
Example: A larger peak on a GLC chromatogram indicates a greater quantity of that compound in the mixture.