Application of UNIFAC models to partition coefficients of biochemicals between water and n-octanol or n-butanol

The objective of this work is to examine whether the various UNIFAC models can represent phase behavior of biochemicals in the dilution solution such as partition coefficients (log Pi). Especially, the log Pi of a solute in the n-octanol/water system was used as main target for the examination in this work. First, the log Pi of common chemical solutes was tested by use of various UNIFAC models. It was concluded that the original model and Larsen et al.ʹs model [B.L. Larsen, P. Rasmussen, Aa. Fredenslund, Ind. Eng. Chem. Res., 26 (1987) 2274–2286] were suitable for the prediction of the log Pi. In the next, both models were applied to calculation of log Pi of biochemicals such as amino acids, their derivatives, and sugars. In addition, hydrophobicity constants (π) of an amino acid side chains were calculated from the log Pi of amino acids. From the above results, the performance of the UNIFAC models for log Pi and π was discussed.