Development and Validation of a Stability Indicating HPLC Assay Method for Determination of Warfarin Sodium in Tablet Formulation

The objective of the current study was to developed simple, precise and accurate isocratic reversed-phase stability indicating high performance liquid chromatography [HPLC] assay method validated the for determination of warfarin in solid pharmaceutical dosage forms. Isocratic reversed phase high performance liquid chromatography [RP-HPLC] separation was achieved on a SGE SS wakosil (150 mm × 4.6 mm i.d., C8RS 5 µm particle size) column using mobile phase of acetonitrile and 50 mM sodium hydrogen phosphate dibasic dihydrate buffer pH 3.0 (50:50 v/v) at a flow rate of 1.0 mL min-1, the injection volume was 20.0 μL and the detection was carried out at 280 nm using photo-diode array detector. The drug was subjected to oxidation, hydrolysis, photolysis and heat in order to apply stress condition. The method was validated for specificity, linearity, precision, accuracy, robustness and solution stability. The method was linear in the drug concentration range of 40-160 μg mL-1 with a correlation coefficient 0.9995. The precision (relative standard deviation RSD) amongst six-sample preparation was 0.22% for repeatability and the intermediate precision [RSD] amongst six-sample preparation was 0.70%. The accuracy (recovery) was between 99.95 and 99.15%. Degradation products produced as a result of stress studies did not interfere with detection of warfarin and the assay can thus be considered stability indicating.