Indo American Journal of Pharmaceutical Research. 2011:1(1);26-33. Simultaneous Estimation of Abacavir Sulfate and Lamivudine in their Combined Dosage Form by First Derivative Zero-Crossing and Ratio First Derivative Spectroscopic Methods *DIPTI RUIKAR, DITI DESAI, BANSARI MYANGAR,*SADHANA RAJPUT Quality Assurance Laboratory, Centre of Relevance and Excellence in Novel Drug Delivery System, Pharmacy Department, G. H. Patel Building, Donor’s Plaza,The Maharaja Sayajirao University of Baroda, Fatehgunj,Vadodara, Gujarat, India – 390 002 Corresponding author Dipti Ruikar G. H. Patel Building, Donor’s Plaza,The Maharaja Sayajirao University of Baroda, Fatehgunj,Vadodara, Gujarat, India – 390 002 e-mail: deeptiruikar@gmail.com Journal home page: http://www.iajpr.com/index.php/en/ INDO AMERICAN JOURNAL OF PHARMACEUTICAL RESEARCH ARTICLE INFO ABSTRACT Article history Received 7 March 2011 Received in revised form 19 March 2011 Accepted 21 March 2011 Available online 26 March 2011 Keywords Abacavir Sulfate Lamivudine First derivative zero crossing Ratio spectra first derivative spectrophotometry. 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. Please cite this article in press as: Dipti Ruikar et al., Simultaneous Estimation of Abacavir Sulfate and Lamivudine in their Combined Dosage Form by First Derivative Zero-Crossing and Ratio First Derivative Spectroscopic Methods. Indo American Journal of Pharm Research. 2011:1(1);26-33.