Impact of ionization and dissociation on partitioning

Generally, the partitioning of ionized species into other than aqueous phases is highly unlikely the apparent distribution is related to the log P values of the non-dissociated form by the following equations for acids and bases, respectively  

The apparent log corresponds to the log P of the unionized compound at pH values p T, for acids or p for bases (log = log Increased ionization due to pH changes results in a linear decrease in the apparent log until another plateau is achieved where only the ionized form determines the partitioning (log P = log The situation becomes 

If a compound has more than one functional group possibly involved in protonation/deprotonation, it is reconunended to calculate p values for each of these and then decide on their relevance for the investigation. In ampholytes such as an aminophenol (or hydroxyaniline depending on the class of compounds under study), both groups may be ionized under environmental conditions and hence both may contribute to the actual speciation of the compound. 

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