HPLC determination of pKa of parabens and investigation on their lipophilicity parameters

An HPLC method is applied for determination of the pKa values and lipophilicity parameter of the most useful preservatives in drugs oral solution formulations at different pH ranges. The same method is used for investigation on the lipophilicity of these compounds. The pKa and lipophilicity parameter values are the most important parameters characterizing the processes of penetration of the preservatives through the cellular membrane at different conditions. The higher lipophilicity contributes to better interaction of the preservatives with the membrane of undesirable microorganisms and assures their biological action.