Removal of polyethylene glycol from proteins by salt-induced phase separation

The use of poly(ethylene glycol) in the purification of plasma and cellular protein is somewhat complicated by the difficulty of removing it from the protein product. The method presented here, quickly and efficiently removes over 95% of the PEG by the simple addition of salts to induce an aqueous two-phase separation with the PEG in the upper phase and greater than 90% of the protein in the lower phase.