purity is so bad after elution from GST column - (May/03/2010 )

NP40 (Igepal) is just another non-ionic detergent. If you've got triton already, you don't need it.

Also, when you go to elute from your nickle column, take a series of elution fractions. I've often seen multiple bands disappear in the later fractions. Also some of the bands might very well disappear after the subsequent GST protocol.
Good luck.