cobalt resin - (Aug/02/2010 )

Hellow everybody...

I use the cobalt resin for his-tagged protein purification. lately I noticed that when I'm concentrating my protein by Amicon Ultra Centrifugal filter Device, there are leftovers of cobalt (there is a pink precipitant
at the bottom) and my concentrated protein solution is pink.

I would like to know how can I get rid of the cobalt leftovers.

edta may help.