pKa/Log P/Log D

Industry standard methods for measurement of ionization constants (pKa) are used. Up to 10 overlapping pKas can be analyzed and protogenic counter-ions are distinguished. Sparingly soluble compounds may be analyzed in mixtures of an organic solvent and the aqueous pKa is extrapolated. The potentiometric and spectrophotometric methods that are used have measured pKa values as low as 1.0 and as high as 13.0.

Lipophilicity is measured with octanol/water and other partitioning media such as cyclohexane, heptane, and liposomes. Log P is a measure of lipophilicity, or the ratio of compound that partitions between octanol and water. As the value increases, so does the lipophilicity of the compound. The determination is based on potentiometric titration, with results comparable to the shake flask technique. Results are reported using the lipophilicity profile, a plot of log D versus pH/Log P is routinely measured between -2 and 5. Potentiometric titration is useful for zwitterions and ion-pairing. Formation of micro-emulsions is easily overcome with this method.

When requesting pKa/Log P/Log D analyses, please use the pKa/Log P/Log D Submittal Form.