The purification of intracellular human recombinant interferon-alpha2b (IFN-alpha 2b) from Escherichia coil (E. coil) was studied using alcohol/salt aqueous two-phase system (ATPS). The influences of nine biphasic systems comprising alcohol-based top phase (ethanol, 1-propanol and 2-propanol) and salt-based bottom phase (ammonium sulfate, di-potassium hydrogen phosphate and monosodium citrate) on IFN-alpha 2b purification were studied. The results showed that the optimum condition for purification of IFN-alpha 2b was achieved in ATPS composed of 18% (w/w) 2-propanol with 22% (w/w) ammonium sulfate in the presence of 1% (w/w) sodium chloride (NaCl). The purified IFN-alpha 2b recorded a purification factor (P-F) of 16.24 with the yield of 74.64%. (C) 2013 Elsevier B.V. All rights reserved.