Strategic method development for praziquantel impurity analysis using analytical QbD framework

In this study, we employed Analytical Quality by Design (AQbD) principles to develop a stability-indicating HPLC method for quantifying three process-related impurities in Praziquantel API samples. Forced degradation experiments provided essential early data, which were assessed through risk analysis and multivariate techniques. Risk assessment was conducted using a hybrid approach that combined an Ishikawa diagram and Failure Mode and Effects Analysis. This process helped identify the critical method parameters for the study, namely: the initial % acetonitrile content, the gradient slope, the flow rate and the column temperature. A two-level Plackett-Burman design was used to identify key method parameters, followed by optimization using a Box-Behnken design. The method's operable design region (MODR) was defined by establishing a robust zone using Monte Carlo simulations and capability analysis. Optimal separation was achieved with a linear gradient elution of water and acetonitrile, a flow rate of 1 mL/min, and a column temperature of 25 °C. Method validation aligned with ICH guidelines, showing determination coefficients above 0.998 and recoveries between 90.2 % and 113.2 %. Repeatability and intermediate precision exhibited RSD values below 6.6 %, and detection limits ranged from 0.07 to 0.15 μg/mL, which met the method's requirements. This method was successfully applied to analyzing Praziquantel API samples.