Study of organic compounds–water interactions by partition in aqueous two-phase systems

• Partition coefficients of fourteen organic compounds were determined in 10–20 ATPS.
• Solute-specific coefficients for the compounds examined were determined.
• The partition behavior for the compounds is affected by dipole–ion interactions.
• Partition ratios values for the compounds can be predicted.
• The solute-specific coefficients can be used in QSAR to describe their odor detection threshold.

Partition coefficients of fourteen organic compounds were determined in 10 or 20 different polymer/polymer aqueous two-phase systems (ATPS) all at physiological pH (0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4). Solute-specific coefficients characterizing different types of solute–water interactions for the compounds examined were determined by the multiple linear regression analysis. It is shown that (i) the partition behavior for the polar organic compounds is affected not only by dipole–dipole and hydrogen-bond interactions with aqueous environment but, notably, in most cases also by dipole–ion interactions; (ii) it is possible to predict partition behavior for compounds with pre-determined solute-specific coefficients in ATPS with characterized solvent features; and (iii) linear combinations of the solute-specific coefficients for the organic compounds might be useful in the development of quantitative structure–activity relationship (QSAR) analysis to describe their odor detection threshold.