Impurity profiling of dapsone using gradient HPLC method

Abstract The quality control of active pharmaceutical ingredients (APIs) is a very important aspect for drug products entering the market. However, also for the well-established drugs, there ought to be a state-of-the-art impurity control. Some of the pharmacopoeial tests for related substances still make use of thin layer chromatography, even though selectivity and sensitivity are suboptimal. Here, we report on the development of a new gradient high performance liquid chromatography (HPLC) method for dapsone in order to replace the currently described pharmacopoeial TLC method. The separation of all relevant components was achieved on a C18 stationary phase (Waters XTerra® RP18 5 μm 4.6 × 250 mm) using a water-acetonitrile gradient. A limit of detection (LOD) of 0.02% was registered for all specified impurities. Additionally, within this study an “impurity of an impurity” was identified by means of LC–MS/MS.