Determination of lamivudine and zidovudine in binary mixtures using first derivative spectrophotometric, first derivative of the ratio-spectra and high-performance liquid chromatography-UV methods

Three methods are presented for the simultaneous determination of lamivudine and zidovudine. The first method depends on first derivative UV spectrophotometry, with zero-crossing and peak-to-base measurement. The first derivative amplitudes at 265.6 and 271.6 nm were selected for the assay of lamivudine and zidovudine, respectively. The second method depends on first derivative of the ratio-spectra by measurements of the amplitudes at 239.5 and 245.3 nm for lamivudine and 225.1 and 251.5 nm for zidovudine. Calibration graphs were established for 1-50 μg/ml for lamivudine and 2-100 μg/ml for zidovudine. In the third method (HPLC), a reversed-phase column with a mobile phase of methanol:water:acetonitrile (70:20:10 (v/v/v)) at 0.9 ml/min flow rate was used to separate both compounds with a detection of 265.0 nm. Linearity was obtained in the concentration range of 0.025-50 μg/ml for lamivudine and 0.15-50 μg/ml for zidovudine. All of the proposed methods have been extensively validated. These methods allow a number of cost and time saving benefits. The described methods can be readily utilized for analysis of pharmaceutical formulations. There was no significant difference between the performance of all of the proposed methods regarding the mean values and standard deviations. The described HPLC method showed to be appropriate for simultaneous determination of lamivudine and zidovudine in human serum samples.