Spectrophotometric Methods for Simultaneous Estimation of Thiocolchicoside and Diclofenac Sodium in Their Combined Dosage Form

Two simple spectrophotometric methods have been developed for simultaneous estimation of Thiocolchicoside and Diclofenac Sodium from pharmaceutical dosage form. Method I is an Absorbance correction method in which absorbance is measured at two wavelengths, 371 nm at which Diclofenac has no absorbance and 248.5 nm at which both the drugs have considerable absorbance. Method II is dual wavelength method which involves estimation of Diclofenac Sodium by plotting difference in absorbance at 248 nm and 268 nm (difference is zero for THC) against its respective concentration. THC was measured at 371nm (Diclofenac Sodium has no absorbance). Both the methods were found linear between the range of 2–16μg/ml for Thiocolchicoside and 12.5–100μg/ml for Diclofenac Sodium. The accuracy and precision were determined and found to comply with ICH guidelines. Both the methods showed good reproducibility and recovery with % RSD in the desired range. The methods were found to be rapid, specific, precise and accurate and can be successfully applied for the routine analysis of Thiocolchicoside and Diclofenac Sodium in their combined tablet dosage form.