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.