Separation and purification Flashcards
What is extraction?
solute transferred from one solvent and placed in another
What is chromatography?
separation of a mixture of compounds by their distribution between two phases (stationary/moving)
What is gas-liquid chromatography?
A liquid (stationary phase) is absorbed into an inert solid.
Sample being analysed is injected in the direction of an inert gas flow (mobile phase) towards stationary phase
As the sample migrates through the column, certain molecules move faster than others allowing separation
Once the molecules reach the end of the column, special detectors signal their arrival.
What is the process of thin-layer chromatography?
A type of finely divided polar material (silica gel/ alumina) is thinly coated onto a glass plate.
Molecules with functional groups of greater polarity will bind more strongly to the stationary phase and not rise as high on the glass plate.
Organic molecules interact with the mobile phase (a solvent). The more polar the solvent, the more easily it will dissolve polar molecules.
The mobile phase will usually contain ethanol, benzene, chloroform or acetone.
There is a dynamic distribution equilibrium between the phases. The different molecules will rise to different heights on the plate.
Their presence can be detected using special stains or UV light.
What is distillation?
the process by which components are separated based on their different boiling points
How do you improve distillation?
by repeating the process over and over
How do you avoid overheating during distillation?
Boiling chips
Slower boiling
Using a vacuum (decreases the vapour pressure)
What is recrystallisation?
A solid organic compound with impurity can be dissolved in a hot solvent and then cool slowly to recrystallise in pure form
The impurities are left behind in the solvent.
