Gas chromatography (GC) separates substances by carrying a vaporised sample through a column using a gaseous mobile phase. It can be used with gases, volatile liquids and substances introduced in vapour form.
| Phase | In gas chromatography |
|---|---|
| Mobile phase | An inert carrier gas, such as helium or nitrogen, transports the sample through the column. |
| Stationary phase | A solid, or a liquid coating held on a solid support. In gas-liquid chromatography the stationary phase is a non-volatile, high-boiling liquid supported on a solid. |
The carrier gas is chemically unreactive under the operating conditions, so it can transport the substances being separated without reacting with them.
GC apparatus
What happens?
- The flow of carrier gas is controlled.
- The sample is injected and forms a vapour.
- The gas stream carries the sample through the column under pressure at high temperature.
- The components separate while moving through the stationary phase.
- As each component reaches the detector, its response contributes to the chromatogram.