Simultaneous quantitative determination of diazepam and liposomes using differential pulse polarography Original Research Article

The need for evaluating the retention of drugs in liposomes has lead to development of a new methodology, based on the differential pulse polarography (DPP), for the simultaneous quantitative determination of non-entrapped diazepam (DZP) and PC liposomes in a buffered solution, pH 7.4, at 37°C. It was found that DZP polarographic signal depends both on liposome concentration and liposome size. Calibration plots of the DZP concentration vs. the current intensity in the presence of different lipid concentration were constructed. The liposome and DZP concentration were determined using these plots and the “standard addition” technique. The DPP detection limit for DZP was found to be 15 μg l−1 while for liposomes in samples with 6 mg l−1 DZP was calculated to be 0.01 mg ml−1.