Has anyone encountered a situation where the protein loaded onto an anion exchange column never (apparently) comes off?
I have tried both a MonoQ column (Quartenary Ammonium groups - a strong anion exchanger) and a DEAE column (weak anion exchanger)and in both cases have observed the same phenomenon. The first few times I run my protein sample through, I recover the protein in a reasonable quantity, but with successive runs the peaks become gradually smaller until the protein stops eluting altogether. At the point where this particular protein is no longer eluting, the column still behaves normally for other proteins, including my protein standards.
I would be interested to know if anyone else has experienced this problem and/or can suggest a solution, because its driving me crazy.

Thanks!

It wouldnīt be normal if protein analysis didnīt drive you crazy. I do not have experience with IC of proteins, but from RP and SEC/GPC labors I would guess that your protein is not too happy in your mobile phase, you probably loose some from the beginning, later injections may then attach to the previous deposits...... hypothetically.
(Problems due to potentially loosing material are among the reasons for wanting to predict peak areas as discussed in an earlier chain)

Hi Cheryl, perhaps your target protein has some hydrophobic groups, in your sample might be something which at first will bind to the surface of your IEC, and than your protein will bind to that substance. How do you rins your column after each run? I would recommend to rinse if possible with water, or better 20% Methanol, or 20% Ethanol. Also 20% Isopropanol is possible, but you should check backpressure. I have no experience if MonoQ will survive this procedure, our resins have no problem with that. Hope this helps. Gerhard