Difference Spectrophotometric Method for the Determination of Duloxetine in Bulk and Tablet Dosage Form

A new, simple, rapid, sensitive and economical spectrophotometric method has been developed and validated for estimation of duloxetine in pure and its pharmaceutical formulation like tablet. During the development of formulations containing duloxetine in its solid dosage form, analytical methods will serve as assay method for quantitation of the duloxetine during product developmental stages. The present work consist of estimation of duloxetine by difference spectrophotometry which is based on shifting of λ max by changing the pH of the solution by adding 1M HCl and 1M NaOH the absorption maximum was obtained. Linearity of the response was demonstrated for the drug for a range fulfilling Beer's law, which is 11–16 μg/ml with the linear regression value of 0.995. The absorption maxima of duloxetine were obtained at 230 nm in 1M NaOH, and in 1M HCl. The results of analysis have been validated statistically and by recovery studies. Interday and Intraday studies showed high degree of repeatability. Recoveries obtained do not differ significantly from 100%. The method was extended to pharmaceutical formulation and there were no interferences from any excipients and diluents. The full analytical validation was performed according to International Conference on Harmonization Q2R1 guidelines for validation of analytical procedures was found to be satisfactory.