Quality by design-based development and validation of a robust RP-HPLC method for the simultaneous estimation of nirmatrelvir and ritonavir in pharmaceutical formulations

The current research sought to design and evaluate a robust, risk-based HPLC technique for the simultaneous quantification of Nir (Nir) and Ritonavir (Rit) in pharmaceutical formulations, using a Quality by Design (QbD) framework. QbD stresses the need of structured experimental design for systematically assessing risks and understanding how important technique factors interact with one other. Materials and Methods: We used an Agilent C18 column (150 mm × 4.6 mm, 5 µm) to separate the compounds by chromatography. The mobile phase was 0.1 % orthophosphoric acid (pH 4.8) and acetonitrile in a 60:40 ratio, with a flow rate of 0.9 mL/min. A PDA detector was used to find the signal at 238 nm, and the column was kept at 29 °C. The average retention times for Nir and Rit were 2.218 min and 2.987 min, respectively. Results: We used a central composite design (CCD) to find the best values for three important factors: the composition of the mobile phase, the flow velocity, and the temperature. The best retention times were 2.307 min for Nir and 2.863 min for Rit. The approach showed great accuracy, with %RSD values of 0.7 % and 0.8 % and recovery rates of 99.95 % and 99.97 %, respectively. Regression equations showed that the approach was quite linear, and shorter run durations made it good for regular quality control. Conclusion: The QbD-driven technique provided extensive insights into the influence of chromatographic variables on method performance. The Design Expert 13.0 model properly showed how important method parameters and responses are related to each other. This made sure that the HPLC approach that was developed was reliable and strong enough to measure both Nir and Rit at the same time in both bulk and dose forms.