thin layer chromatography Flashcards
what is TLC chromatography?
a method that separates compounds on the basis of different polarity.
what is the silica gel?
TLC plates have a thin layer of silica gel spread out on a glass surface. silicon atoms are joined to oxygen atoms in a giant covalent structure.
the silica gel will cause the components of the mixture to separate
what is the stationary and mobile phase?
the stationary phase is the is the silica gel
the mobile phase is a mixture of non-polar or polar solvents
what is the method of TLC chromatography?
- prepare the tlc plate and a pencil line is drawn near the bottom
- drop of solution of the dye mixture is placed on it
- when the spot of mixture is dry, the plate is stood in a layer of solvent below the pencil line and is covered on top with a lid
- the solvent will travel up the plate
advantages of TLC?
pros
- tlc results are more reproducible
- easier to use
- separation is more efficient
- mobile phase moves more evenly through the stationary phase
formula to calculate the Rf value?
Rf = distance moved by the compound/ distance moved by the solvent front
why is iodine used in tlc?
allows to carry a marked version of a tlc run rather than having a pencil sketch the spots in the UV viewer
why is UV light used in tlc?
is used to identify the spots on a tlc plate as it is easy and non destructive
common on colourless spots
why is ninhydrin used in tlc?
since amino acids are colourless compounds ninhydrin is used for detecting them. tlc plate is sprayed and dried in an oven at 105c for 5 mins
how is tlc chromatography different from paper chromatography?
the station phase of tlc is a glass plate coated with silica gel whereas paper is water trapped in filter paper
tlc is faster, detects smaller amounts and is better at separating less polar compounds
whereas paper is cheaper, requires little prep and is more efficient for polar and water soluble compounds
