Chomotography Flashcards
What is chomotography?
A separation method that separates components in a mixture that have different solubilities.
What is a mobile phase?
This is the part that has molecules that can move. This is usually a liquid or gas.
What is a stationary phase?
This is the part where the molecules can’t move. This can either be a solid, liquid or a solid support.
Describe the general idea behind chromatography.
The substances that are more soluble in the mobile phase move further up than the ones that are more strongly adsorbed to the stationary phase.
What is the mobile and stationary phase in thin-layer chromatography?
M: A liquid solvent like ethanol
S: A thin layer of silica (silicon dioxide) fixed to the metal plate.
Describe how to separate a mixture using TLC.
- Draw a line near the bottom of the TLC plate.
- Using a capillary tube put a very small drop of the mixture that needs to be separated on the line.
- Make sure to mark where you put the spot.
- Add the solvent to a chamber or large beaker.
- Make sure that the solvent does not have a depth greater than 1 cm3 and put a lid on top of the chamber.
- Place the TLC plate into the chamber, making sure the solvent line is below the baseline.
- Replace the lid to make sure there is a tight seal.
- When the level of the solvent is 1 cm3 from the top of the TLC plate remove the plate and mark the solvent level with a pencil.
- Allow the plate to dry in a fume cupboard.
- Place the plate under a UV lamp to see the spots and draw around them with a pencil.
- Calculate the Rf values.
Why must you wear gloves when drawing the pencil line?
To prevent contamination from the hands to the plate.
Why must you use a pencil to draw lines?
It will not dissolve in the solvent.
Why must you place a lid on the beaker?
To stop the toxic solvent from dissolving.
Why must the plate be dried in a fume cupboard?
The solvent is toxic.
Why is a UV lamp used to see the spots?
They are colourless and not visible.
