Separation of Closely Eluting Impurities by Selecting Appropriate Stationary Phase

HPLC column is the heart of HPLC hence selecting the appropriate stationary phase is the most important part of method development. The selection of the stationary phase plays an important role in selectivity. There are numbers of regulatory queries on the inappropriate resolution between closely eluting impurity hence it is important to develop the suitable stability-indicating analytical method. There are more complex drug products hence analytical scientists need to develop the specific, accurate, precise and robust method to attain the optimum resolution between closely eluting impurities.  Adequate resolution and recovery between the closely eluting peaks are the definitive goals for good chromatography. The resolution, means the distance between the center of two peaks measured by the retention time or volume divided by the average width of the individual peaks.

USFDA recommends the resolution should be more than 2. If there are closely eluting peaks in the method then it is essential to give minimum resolution criteria between the two peaks.