Expression of Partition Coefficients

 In biochemical applications, partition coefficients are often expressed in terms of an octanol/water coefficient or Ko/w—i.e., the ratio at equilibrium of the concentration of a nonionized organic compound in an organic solvent (e.g., octanol) versus the concentration of the compound in water. Ko/w has been correlated with oleophilicity, the affinity of a compound to an oleophilic environment; compounds having a Ko/w value > 1 are oleophilic while those < 1 are hydrophilic. Ko/w thus provides an important predictive measure of the ability of a compound to pass through the skin’s acid mantle and permeate the oleophilic membranes of cells in the epidermis and dermis.