Chapter 33 (Chromatography) Flashcards
What is chromatography?
An analytic technique that separate component in a mixture between a mobile phase and a stationary phase.
What is the mobile phase?
The solvent
What is the stationary phase?
The inert substance that is in the suspension.
What is thin layer chromatography?
When a thin plate is coated with a solid solvent.
How is rf value calculated?
distance moved by amino acid/distance moved by solid
What is the method for thin layer chromatography?
1) Wear gloves and draw a pencil line 1 cm above the bottom of the TLC plate and mark spots for each sample equally placed along the line.
2) Use a capillary tube to add a tiny drop of each solution to a different spot and allow the plate to air dry.
3) Add solvent to a chamber or large beaker with a lid so that is no more than 1cm.
4) Place the TLC plate into the chamber, making sure than the solvent is below the pencil line. Replace the lid to get a tight seal.
5) When the solvent reaches about 1 cm from the top of the plate, remove the plate and mark the solvent level with a pencil. Allow the plate to dry in a fume cupboard.
6) Place the plate under a UV lamp in order to see the spots. Draw around them lightly in pencil.
7) Calculate Rf values of the observed spots.
Why are gloves worn for TLC?
To prevent contamination from hands to plate.
Why is a pencil line drawn?
Will not dissolve in the solvent.
Why is the depth of the solvent below the origin line?
If the solvent is above the origin line it will dissolve the sample spots from the spots.
How is the Rf value made more accurate?
Allow the solvent to rise to the near the top of the plate.
Why is the solvent dries in a fume cupboard?
The solvent is toxic.
Why is a UV lamp used to see the spots?
They are colourless and not visible.
How does a solid stationary phase separate?
Adsorption
How is a liquid stationary phase separated?
Relative solubility
