New aqueous two phase system comprising polyethylene glycol and xanthan

A new aqueous two phase system comprising polyethylene glycol and xanthan is reported together with its phase diagram. The phase composition of the bottom phase did not vary (PEG 1.6-1.8% w/w; xanthan 0.24-0.28% w/w) while that of the top phase varied significantly (PEG 4-5% w/w, xanthan 0.05-1.37% w/w). Unlike conventional aqueous two phase systems, the viscosity of the top phase is also high and values are comparable to that of the bottom phase. When BSA was used as a model protein, it partitioned entirely into the bottom phase.