Indicate which will emerge FIRST from a column of the specified solid phase support

GLU-VAL and ASP-GLY from a column of amine-modified cellulose, eluted with a butanol-acetic acid-water buffer of progressively decreasing pH

A. GLU-VAL

B. ASP-GLY

C. both emerge simultaneously

D. neither can be eluted


I know the answer is c. I understand that both GLU-VAL and ASP-GLY have one polar and one non-polar residue so this would equal out their attraction ratios for the amine-modified cellulose.

I just want to understand the reasoning for why one isn't above the other.

Is it because since the pH is decreasing, the amine-modified cellulose is protonated? This could cause the C=O of the glutamic acid and aspartic acid to form a seemingly equal attraction to the protonated amine group? If so does this mean that the GLY and VAL have no effect at all in this???