In ion exchange chromatography, the concentration of salt in the buffer running over the column is crucial. The column contains beads with either positive or negative charges. In a low salt environment, proteins with the charge opposite of the beads will stick to the column. As more and more salt is added, the salt ions displace the proteins binding to the column, and the proteins come off of the column (elute).
In the screenshot below, you see the elution profile from an ion exchange column. The line that starts out grey, and then turns green and purple in the peaks, reflects the absorbance at 280 nm. The initial grey plateau shown on the graph occurs because many of the proteins didn’t bind to the column at all; they just went through. The blue line on the graph reflects the salt concentration. Elution begins when the blue line (salt concentration) starts going up.
© GE Healthcare - All rights reserved
GE Healthcare UK Limited
Amersham Place
Little Chalfont
Buckinghamshire
England HP7 9NA