Simultaneous Estimation of Abacavir Sulfate and Lamivudine in their Combined Dosage Form by First Derivative Zero-Crossing and Ratio First Derivative Spectroscopic Methods

Two simple, sensitive, specific and accurate spectrophotometric methods are proposed in the present work for the simultaneous estimation of Abacavir sulfate (ABA) and Lamivudine (LMV) in their binary mixture. In first derivative zero crossing technique the absorbances at 234.2 nm (zero crossing point of LMV) were plotted against the respective concentrations of ABA. Similarly the absorbances at 287.3 nm (zero crossing point of ABA) were plotted against the respective concentrations of LMV. For the ratio spectra first derivative spectrophotometric method, the graphical treatment of the overlapping spectra depends on division of the absorption spectrum of the binary mixture by a standard spectrum of one of the components and then the first derivative amplitudes measured at 233.0nm for ABA and 236.4nm for LMV .The calibration curves follow Beer’s law in the range of 5 to 30 μg/ml for ABA and 2.5 to 15 μg/ml LMV for both the methods. The methods were successfully applied to quantify ABA combined with LMV in tablets and validated accordingly