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Experimental results for the partition coefficient of 41 substances (several phenol, indole, biphenyl, and naphthalene derivates, polycyclic aromatic compounds, and polyfunctional haloaromatics) in hexane + water at 298.15 K are reported. Partition coefficients were measured by reversed phase high-performance liquid chromatography and the shake-flask method. The experimental results are compared successfully to predictions by the linear solvation energy relationship method.

Partition coefficients PO,w ((i)) describing the distribution of a solute i onto coexisting phases of 1-octanol and water are needed in a large variety of applications. They can be measured directly by HPLC as long as log PO,w ((i))≧ 3.5. For more hydrophobic substances, several experimental procedures have been proposed in the literature. The reliability of those methods is questionable. Therefore, in the present work, PO,w ((i)) is determined experimentally by three HPLC methods using reversed-phase HPLC [1]. Results from different procedures are compared critically. The method of Braumann [2] proved to be superior over the OECD-guidelines [3]. It was therefore applied to determine octanol/water partition coefficients for 23 substances at 25 °C. For eight of those substances (4-methylindole; 9-(hydroxymethyl)anthracene; N-ethylcarbazol; ethylcyclohexane; trans-2-octene; l,l-dimethyl-(ethy])cyclohexane; heptylbenzene; 4-dodecyl-l,3-benzenediol) no experimentally determined number for PO,w ((i)) has been published before.

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