Stability Indicating Spectrophotometric and Spectrodensitometric Methods for Determination of Calcium Dobesilate in the Presence of Its Impurity And/or Degradation Product

Objective: To develop Two simple, specific, accurate and precise methods for determination of calcium dobesilate (CD) in the presence of its impurity and / or degradation product namely hydroquinone (HQ). Methods: Method A is an extended ratio subtraction one (EXRSM), while method B is a HPTLC-densitometric one using benzene: methanol: ethyl acetate: sodium lauryl sulphate (7: 2.5: 2: 0.05 v/v/v/w) as a developping system. Results: The developed methods were successfully applied for determination of CD in the assay of raw material and tablets as well as quantitative determination of HQ with standard deviation values less than 1.5. The two methods are linear over the concentration range of 5-70 μg. mL−1 for CD, and 5-60 μg. mL−1 for HQ, methods were validated as per ICH guidelines; accuracy, precision and repeatability are found to be within the acceptable limits. Conclusion: The two developed extended ratio subtraction method (EXRSM) and the HPTLC-densitometric one are valid for application in laboratories lacking liquid chromatographic instruments.