Consider that you wish to separate a mixture of glutamate, glycine and lysine by ion exchange chromatography.

Using a cation exchange column at pH 5, which amino acid would you expect to elute first and which last?

pKa and pI values are as follows:

Glutamate: pK₁ = 2.19, pK₂ = 9.67, pK_R = 4.25, pI = 3.22

Glycine: pK₁ = 2.34, pK₂ = 9.62, pI = 5.97

Lysine: pK₁ = 2.18, pK₂ = 8.95, pK_R = 10.53, pI = 9.74