Using column chromatography as an example, explain how components of a mixture interact with the stationary and mobile phases, and explain how the separation of the components is achieved?

Under certain conditions, proteinogenic $2$-amino acids have the following retention factors:

histidine   $0.11$        lysine    $0.14$

glycine    $0.26$          serine   $0.27$

alanine  $0.38$          cysteine   $0.40$

tyrosine  $0.45$         asparagine    $0.50$

valine   $0.61$          leucine         $0.72$

A paper chromatogram of a mixture of unknown $2$-amino acids showed three spots at distances $10, 28$ and $35 \mathrm{mm}$ from the start line. Identify the amino acids if the distance between the start line and the solvent front was $70 \mathrm{mm}$.

The given figure represents a thin layer chromatogram of an amino acid. 

Outline the principle of thin layer chromatography. Refer in your answer to the nature of the mobile and stationary phases.