A Simple Method Based on One Phase Measurement for Determination of the Octanol-Water Partition Coefficient of Drugs

The octanol-water partition coefficient (P-ow) is widely used to assessment of lipophilicity of drug. The P-ow can be measured by determining the ratio of the concentration of the drug in octanol to its concentration in water at equilibrium. In the standard method, two calibration curves are required in order to obtain the concentration of drug in the two phases. The procedure is thus tedious and time consuming. In this work, a simple approach for determining the P-ow of drug is described. Only the absorbance of one phase and volumes of octanol and water are used in the calculation; calibration curves are no longer required, making the procedure much more convenient. The method was applied to examples of hydrophobic and hydrophilic drugs. The P-ow values obtained by our method agreed well with literature values (R-2 = 0.998). This method is simple and capable for screening new drugs in a stage of drug discovery.