Nickle column and His-tagged protein purification - recharging Ni+2 column (Apr/24/2002 )

I was trying to recharge a Ni+2 column (originally bought from Invitrogen) to reuse it for purification of my His-tagged protein. The column was originally pepared with NiCl2 solution ( as per Invitrogen). I want to know if I can recharge this column using NiSO4 instead of NiCl2 and if so, at what concentration. Invitrogen suggests using 5mg/ml of NiCl2 i.e. around 0.02M . But people make NiSO4 columns with 0.1M NiSO4.
Thanks
Mani