3.3.16 Chromatography Flashcards
What is chromatography?
It can be used to separate and identify the components in a mixture based on the affinity to the stationary and mobile phase.
What are the 3 types of chromatography?
Thin-layer chromatography
Column chromatography
Gas chromatography
What is thin-layer chromatography (TLC)?
A plate is coated with a solid and a solvent moves up the plate.
What is column chromatography (CC)?
A column is packed with a solid and a solvent moves down the column.
Wha is gas chromatography?
A column is packed with a solid or with a solid coated by a liquid, and a gas is passed through the column under pressure at a high temperature.
What is the stationary and the mobile phase in thin-layer chromatography?
Stationary phase- chromatography paper
Mobile phase- solvent
Describe how to set up TLC and how it works.
Place a small spot of mixture to be analysed.
Dip the paper in solvent.
Each component dissolves in the solvent.
The solvent moves up the paper
The more soluble a component is, the further it moves.
What is the stationary and mobile phase in GC?
Stationary phase- liquid absorbed in an inert solid support
Mobile phase- gas
Describe the method of GC.
A small amount of the sample is injected into the machine.
The injector is contained in an oven. The sample boils and is carried along a thin column by an inert gas carrier.
The column contains the liquid stationary phase absorbed onto an inert solid, the time taken to through the tube will depend upon time moved with gas rather than attaching to the liquid.
What is retention time?
Time taken for a compound to travel through the column to the detector.
Measured from injection to max peak height.
What 2 factors affect retention time?
↑ boiling point -> ↑retention time
↑ solubility -> ↑ retention time
Which values are used in chromatography to determine the substance?
Retention time
Rf value
Describe how flame ionisation detection works.
The component exits and is burnt in a hydrogen flame, producing ions.
A detector produces electric current.
The more the amount of of the component, the higher the current.
The current in presented by a chromatograph.
How do you interpret a chromatograph produced by flame ionisation detection?
Each compound produces a peak
The area under the peak is proportional to the amount of the compound
What is the stationary and mobile phase in column chromatography?
Stationary phase- silica
Mobile phase- suitable organic solvent
