I don't think there is a problem with magnesium ion or sulfate ion, as far as the resin is concerned. However, phosphate buffers are often used for IMAC, and magnesium phosphate has low solubility. So the MgSO4 is incompatible with the phosphate buffer, not the resin. If you use a buffer other than phosphate, it should be OK.

Hi there,

According to the joint document magnesium choride has no effect up to 4M (!) on IMAC