Aqueous two-phase systems (ATPS) are biphasic systems composed mainly by water. This kind of systems have been successfully applied for the separation of different kinds of solutes, such as metal ions [1], proteins, DNA and RNA [2], cells or viruses. Tn recent years, considerable interest has arisen concerning the behavior oftetraalkylammonium salts in aqueous solution, particularly with regard to their anomalous thermodynamic behavior, hydration, and apparent structure-promoting influence in water. So far, many thermodynamic and spectroscopic studies have indicated the concept of "structure maker" appropriate for a tetrabutylammonium bromide (TBAB) ion. Lee et al. [3] determined the liquid-liquid equilibrium (LLE) behavior of TBAB, benzene, and water mixture. However, data for the phase diagram of the TBAB + salt + water systems have not been reported at present. In this work, we reported LLE data for the TBAB+ kosmotropic salts (Na3P04, Na2C03, Na2S04, NaH2P04, Na2HP04 and Na3-citrate) ATPSs.
