Binodal curves and tie-lines were determined for two different PEG-sodium citrate ATPSs, at T = 298.15 K.
Merchuk equation was applied for the binodal curve fitting.
New partition coefficients for four DNP-amino acids were measured, at T = 298.15 K.
The relative hydrophobicity of the conjugated phases was calculated and considered in terms of the Gibbs energy of transfer of a methylene group.
The influence of the PEG molecular weight on the phase formation and solute partitioning was discussed.