DETERMINATION OF LogP BY THE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD

Abstract

The partition coefficient (P) characterizes the tendency of a neutral (uncharged) compound to distribute between two immiscible phases consisting of a lipid phase (fats, oils, organic solvents) and water. The partition coefficient is an important measurement of the physical nature of a substance and thereby a predictor of its behavior in different environments. The logP value provides an indication of whether a substance is likely to be absorbed by plants, animals, humans, or other living tissues, or alternatively to be readily transported and dispersed by water.

 The high-performance liquid chromatography (HPLC) method enables partition coefficients to be estimated in the logP range between 0 and 6. The method is not applicable to strong acids and bases, metal complexes, substances which react with the eluent, or surface-active agents. The inter-laboratory comparison test has shown that with the HPLC method logP values can be obtained within ± 0,5 units of the Shake-Flask method values.

A negative value for logP means the compound has a higher affinity for the aqueous phase (it is more hydrophilic); when logP = 0 the compound is equally partitioned between the lipid and aqueous phases; a positive value for logP denotes a higher concentration in the lipid phase (i.e., the compound is more lipophilic). LogP = 1 means there is a 10:1 partitioning in Organic : Aqueous phases.