Comparing types of chromatography: including gas chromatography
I can identify features of different types of chromatography and describe how the techniques are used to separate and identify components of a mixture.
Comparing types of chromatography: including gas chromatography
I can identify features of different types of chromatography and describe how the techniques are used to separate and identify components of a mixture.
Lesson details
Key learning points
- Paper, thin layer (TLC), and gas chromatography (GC) can all distinguish between pure and impure substances.
- Chromatographic processes use a mobile and stationary phase. TLC and GC both use silica/alumina as a stationary phase.
- Thin layer chromatography (TLC) uses locating agents to develop chromatograms and aid analysis of them.
- Chromatograms from gas chromatography (GC) also provide details about the amount of each component in a sample.
- Retention factors (Rf) and retention times both provide quantitative information about a sample's components.
Keywords
Stationary phase - A surface along which the solvent (and any dissolved components) travels. It does not move during chromatography.
Mobile phase - The movement of a solvent and any dissolved components of a sample along the stationary phase in chromatography.
Chromatogram - The resultant pattern of a sample’s components on the stationary phase after chromatography has been carried out.
Thin layer chromatography - A type of chromatography that uses a thin layer of an inert substance spread over an unreactive flat surface as the stationary phase and a liquid state substance for the mobile phase.
Gas chromatography - A type of chromatography that uses an inert substance packed into a coiled tube as the stationary phase and an unreactive/inert gas as the mobile phase.
Common misconception
Students sometimes struggle to understand how using different mobile and/or stationary phases affects the resulting chromatograms.
Perform chromatography of the same mixture using different mobile phases/stationary phases and discuss the pros/cons of each combination.
Equipment
Grass sample, propanone, capillary tube, dropping pipette, mortar and pestle, water, TLC plate, chromatography, 2x beaker, watch glass, paper, pencil, ruler.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Starter quiz
6 Questions
dissolves the solute(s)
furthest point reached by a solvent along the stationary phase
fixed medium through which a solvent, and components it contains, move
a liquid or gas that moves components it contains to separate them out
Exit quiz
6 Questions
helium is often used as the mobile phase
water is typically used as the mobile phase
volatile organic solvents are used as the mobile phase