Determination of duloxetine hydrochloride in the presence of process and degradation impurities by a validated stability-indicating RP-LC method

A stability-indicating gradient reverse phase liquid chromatographic purity and assay method for duloxetine hydrochloride (DUH) was developed and validated. DUH was subjected to the stress conditions and it is sensitive towards oxidative, acid and hydrolytic degradation. Successful separation of DUH from its two process impurities and one degradation impurity formed under stress conditions was achieved on a Symmetry C18, 250 × 4.6 mm, 5 μm column using a gradient mixture of solvent A (0.01 M potassium dihydrogen orthophosphate having 0.2% triethyl amine, pH adjusted to 2.5 with orthophosphoric acid) and solvent B (20:80 v/v mixture of acetonitrile and methanol). The flow rate is 1 ml/min and the detection wavelength is 230 nm. The mass balance was found to be in the range of 99.2–99.7% in all the stressed conditions.