Development and Validation of UV Spectroscopic Method for Simultaneous Estimation of Doxofylline and Terbutaline Sulphate in Combined Dosage Form

Two simple spectrophotometric methods have been developed for simultaneous estimation of Doxofylline and Terbutaline sulphate in tablet dosage form. The method is developed using 0.1M NaOH as a solvent. Method (I) is the Q- absorbance ratio method, two wavelengths are selected, one being the isoabsorptive point 294.1 nm and other being the absorption maxima of Doxofylline at 273 nm. Method (II) is the Absorbance correction method, two wavelengths are selected, one being absorption maxima of Doxofylline at 273 nm and other being the corrected absorbance at 302.96 nm. The Linearity was observed in the concentration range of 10-50 μg/ml for Doxofylline and 2-8 μg/ml for Terbutaline sulphate respectively, correlation coefficient (r 2 < 1). 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 proposed methods can be successfully applied for the routine analysis of both the drugs from tablet dosage form.