- Gas Chromatography (GC) differs from TLC and HPLC by their mobile phase. The mobile phase in GC is an inert gas.
- The sample is is vaporised on injection into the system and is carried through the column by the mobile phase.
- Like all chromatographic techniques it separates complex mixtures for Qualitative and Quantitative analysis.
- The mobile phase in the GC system is an inert, unreactive gas which will not react with the sample or stationary phase.
- The main types of mobile phase used in GC is helium. Nitrogen is commonly used too.
- The stationary phase is a solid inert material which is coated with a solid or liquid. It is then packed into a coiled column.
- The type of stationary phase used depends on the separation required.
Gas Chromatography Instrument
Gas Chromatography Process
- In GC the sample in injected into the column.
- The sample is immediately vaporised and driven through the column (stationary phase) by the mobile phase.
- In the column the component which is most attracted to the stationary phase will be the first component to leave the column and reach the detector. It is then followed by the next component which had a greater affinity for the stationary phase than the mobilt phase.
- The component which leaves the column last is the most attracted to the stationary phase.
- When the components leave the column they arrive at the detector where the information processed is translated to a chromatogram by the software on the computer.
Uses of Gas Chromatography
- GC is the primary technique used in forensic analysis.
- One of its main uses is for testing bodily fluids for:
- Illegal substances,
- It can also be used to identify:
- Residue from explosives,
- Fuels and Solvents used in arson attacks.