Impurity profiling of dapsone using gradient HPLC method

Area of Science:

• Pharmaceutical Analysis
• Analytical Chemistry
• Drug Quality Control

Background:

• Robust quality control of active pharmaceutical ingredients (APIs) is crucial for drug safety and efficacy.
• Existing pharmacopoeial impurity testing methods, such as thin-layer chromatography (TLC), often exhibit suboptimal sensitivity and selectivity.
• There is a need for advanced analytical methods to ensure state-of-the-art impurity control, even for established drugs like dapsone.

Purpose of the Study:

• To develop and validate a novel gradient high performance liquid chromatography (HPLC) method for the analysis of dapsone.
• To replace the current pharmacopoeial TLC method with a more sensitive and selective HPLC technique for impurity profiling.
• To identify and characterize impurities, including potential "impurities of impurities", within dapsone samples.

Main Methods:

• Development of a gradient HPLC method utilizing a C18 stationary phase (Waters XTerra® RP18 5 μm 4.6 × 250 mm).
• Optimization of the mobile phase using a water-acetonitrile gradient for effective separation of dapsone and its related substances.
• Utilized Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) for impurity identification.

Main Results:

• Successful separation of all relevant dapsone-related components was achieved using the developed gradient HPLC method.
• A limit of detection (LOD) of 0.02% was established for all specified impurities, indicating high sensitivity.
• An unknown impurity was identified as an "impurity of an impurity" through LC-MS/MS analysis.

Conclusions:

• The developed gradient HPLC method provides a superior alternative to the pharmacopoeial TLC method for dapsone impurity analysis.
• This new method enhances the sensitivity and selectivity of impurity detection, contributing to improved drug quality control.
• The identification of an "impurity of an impurity" highlights the method's capability in comprehensive impurity profiling.