Proteins usually exist in multiple charge states. Molecules in dufferent charge states would show different retention times or broader peaks, if their conversion is not rapid enough in a chromatographic scale. Has anyone seen broad peaks or multiple peaks for proteins of MW 20K? I understand that proteins have lower difussion efficiency and have broad peaks.

Thanks!

Usually, the equilibration with the mobile phase should get quite rapidly to a defined charge state. If you do not trust in this, dissolve your sample in your mobile phase buffer and see if the peak form changes. If it does, you can make some nice studies and write a paper.

A.Mouse is right, "charge state" equilibration is essentially instantaneous compared to the residence time on the column. Conformational changes in proteins, however, can have longer equilibration times, and this can cause significant peak shape problems.