Chromatography

Question 1

Write a method you would use to carry out chromatography.

Answer 1

1) wearing gloves, draw a pencil line 3cm above bottom of TLC plate and mark spots for each sample, equally spaced along the line.
2) use a capillary tube and add a tiny drop of each solution to the spots and allow the plate to dry
3) add solvent to a beaker which is no more than 1 cm in depth
4) place the TLC plate into the beaker, making sure solvent is below the solvent line. Add lid
5) when solvent reaches 1cm form top of plate, remove plate and mark solvent with pencil line
6) allow plate to dry in fume cupboard
7) look at plate underneath UV light and pencil in dots
8) calculate the Rf values of the spots

Question 2

Why are …. used?

1) gloves
2) pencil
3) specific depth
4) lid
5) fume cupboard

Answer 2

1) avoids cross contamination from hands
2) will not dissolve solvent
3) if sample is too deep, it will dissolve the sample spots
4) o prevent evaporation of toxic solvent
5) solvent is toxic

Question 3

How do you calculate rf value?

Answer 3

Distance moved by amino acid/ distance moved by solvent

Question 4

Why wont some substances separate?

Answer 4

Similar compounds have similar Rf values. Some spots may contain more than one compound