Prac 12 Flashcards
TLC
Wearing gloves, draw a pencil line 1 cm from the bottom of a TLC plate.
Mark spots for each sample, equally spaced along the line.
Use a capillary tube to add a tiny drop of each solution to a different spot and allow the plate to air dry.
Add solvent, no more than 1 cm deep, to a developing tank.
Place the TLC plate into the tank, ensuring that the level of the solvent is below the pencil line. Replace the lid and wait.
When the solvent front has moved to about 1 cm from the top of the plate, remove it from the tank and leave it to dry in a fume cupboard.
Use a UV lamp to highlight the samples and lightly draw around them in pencil.
Calculate the Rf value of each sample and analyze.
Mark everything with a pencil; Why?
it won’t run or smudge.
Why Wear gloves?
Bare hands would contaminate the plate.
Always keep the pencil line and samples above the solvent level Why?
so they don’t dissolve in the solvent layer.
A UV lamp is needed Why?
highlight the sample spots as without them, they are colorless (invisible).
Amino acids are colourless.
Why is a lid important?
prevents escape of vapour (from beaker) / evaporation of solvent (from beaker) * so atmosphere in beaker is saturated with solvent vapour owtte * to reduce evaporation from the plate ALLOW (for bullet point 3) so solvent can rise up plate ALLOW (for bullet point 3) to avoid plate drying out
