Determination of liposomes drug retention capacity using differential pulse polarography: the case of chlorothiazide

Abstract

A methodology based on differential pulse polarography (DPP) was developed for the quantitative, non-destructive determination of the entrapped, adsorbed and free chlorothiazide (CHT) in the presence of liposomes. Results were compared to those obtained from the application of conventional procedure and found equally reliable. Discrimination between adsorbed and free CHT and the capability for non-destructive determination of the entrapped drug were among the advantages of DPP methodology over the currently used technique. From the application of DPP to a 1 mg ml −1, 4.5 μm diameter liposome solution, it was found that drug adsorption was dependent on whether or not drug was entrapped in liposomes, it being twice as large for the empty liposomes. The amount of encapsulated CHT was found to be linearly dependent on the drug concentration, up to 100 mg l −1, present during the encapsulation procedure and stabilized to a maximum when larger CHT concentrations were used.