Question from hw was: a) In what order would the amino acids Arg, His, and Leu be eluted from a carboxymethyl column at pH 6? b) in what order would Glu, Lys, and Val be eluted from a diethylaminoethyl column at pH 8? Answer for a) Leu, His, Arg and b) Lys, Val, and Glu. My question is WHY
For A I figured leucine would be eluted first because it is non polar side chain which will not interact with the stationary phase. Histidine possibly next because it's pKa for side chain is 6.06 which means it won't interact as well with the negative charge on side chain followed by arginine with a higher pK
For B, I honestly would have that valine would go through first with the non polar side chain. But I'm assuming lysine first because the stationary phase is positively charged (I think) and lysine also pos charge will not interact, followed by valine, and Glu with its neg charge will interact with stat phase so it's last.
This is confusing me though I don't know if my reasoning is even right, and why the non polar would go through first in part A but not with part B