Aqueous two-phase (ATP) is an efficient implement for separation
of various substrates [1–5]. By introduction of two kinds of
polymers (PEG and dextran) or one polymer and one salt (PEG and
phosphate salt) into water, two immiscible aqueous phases could
be formed [6]. Each phase of ATP contains one primary polymer
with over 70% water. Due to the low-interfacial tension between
the two conjugated phases, ATP facilitates the separation of biomaterials
such as small molecular compounds [7], proteins [8,9] and
antibiotics [10] without the problem of pH-adjustment and organic
solvent pollution [11].