A simple, accurate and precise dual wavelength spectrophotometric method was developed for simultaneous determination of lamivudine and tenofovir disproxil fumarate in bulk and their combined pharmaceutical dosage form. The principle for dual wavelength method is “the absorbance difference between two points on the mixture spectra is directly proportional to the concentration of the drug component”. Lamivudine shows maximum absorbance at 270 nm and tenofovir disproxil fumarate shows maximum absorbance at 260 nm. In dual wavelength method, two wavelengths were selected for each drug in a way so that the difference in absorbance is zero for another drug. Lamivudine shows equal absorbance at 263.91 and 276.33 nm, where the difference in absorbance was measured for determination of tenofovir disproxil fumarate. Similarly, difference in absorbance at 253.25 and 266.27 nm were measured for determination of lamivudine. 0.1N NaOH was taken as a solvent. Regression analysis of Beer’s plots showed good linearity in concentration range of 10-120 µg/ml for lamivudine and 10-80 µg/ml for tenofovir disproxil fumarate with correlation coefficient 0.999 and 0.997 for LAM and TDF respectively. The mean percent label claim of tablets of lamivudine and tenofovir disproxil fumarate in formulation estimated by the proposed method was found to be 103.57% and 98.46% for LAM and TDF respectively. The developed method was validated according to ICH guidelines and values of accuracy, precision and other statistical parameters were found to be good accordance with the prescribe values. Accuracy of method was found between 95-105% for both the drugs. The precision (intra‐day, inter‐day and repeatability) of method was found within limits for both the drugs. The proposed method was successfully applied for analysis of these drugs in commercial tablets.
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