Chromatography Flashcards
What is chromatography used for?
To separate stuff in a mixture to be able to identify the components
What is the mobile phase?
Where the molecules can move
What phases are involved in the mobile phase?
Always a liquid or a gas
What is the stationary phase?
Where the molecules can’t move
What phases are involved in the stationary phase?
Must be a solid or a liquid on a solid support
What is the basic principle of the chromatography?
The mobile phase moves through or over the stationary phase.
The distance each substance moves depends on its solubility in the mobile phase and its retention by the stationary phase
What happens to components that are more soluble in the mobile phase?
They will travel further than components which are more strongly adsorbed to the stationary phase
What is the mobile phase in TLC?
Solvent such as ethanol
What is the stationary phase in TLC?
A thin layer of silica or alumina fixed to a glass or metal plate
Why must the solvent be below the baseline?
So it doesn’t dissolve the samples
What is the solvent front?
how far the solvent has travelled
Why does the plate have to be placed in a fume cupboard in TLC?
To prevent any toxic or flammable fumes from escaping into the room
What are the two ways of revealing colourless chemicals?
- UV light
- Iodine vapour
How do you reveal colourless chemicals using UV light?
Many TLC plates have special fluorescent dye added to the silica or alumina layer which glows when a UV light Is shined on it and then circles can be drawn around the dark spots of chemical
How do you reveal colourless chemicals using iodine vapour?
It is a locating agent so it sticks to the chemicals and shows them up as purple spots
