Effects of polymer pH and molar mass on the PEG/phosphate aqueous two-phase system

Effects of polymer pH and molar mass on the PEG/phosphate aqueous two-phase system. Liquid-liquid extraction using aqueous two-phase systems (ATPSs) is a promising technique for the purification of biomolecules of industrial and laboratory interest. This work presents a study of the phase diagrams for different poly(ethylene glycol) (PEG) molar masses (ranging from 400 to 4000) and potassium phosphate at pH varying from 6 to 11 in standard conditions. The influence of PEG molecular mass at different pHs was studied from the phase diagrams formed. Stock solutions of PEG 400 and 4000 (100 and 50% w w(-1), respectively) and phosphate (20% w w(-1) KH(2)PO(4)/K(2)HPO(4)) were prepared at the appropriate pH (6, 7, 8 and 9). For pHs 10 and 11, NaOH 1M was used in addition to the salts. The results showed that low concentrations were used to form the ATPS with high molecular mass PEG. On the other hand, there was no pH influence in the equilibrium curves - in other words, a significant shift of the binodal in different pHs.