Abstract

Optimization of a Liquid Chromatography Method for the Analysis of Related Substances using Design of Experiments Integrated with the Steepest Ascent Method and Monte Carlo Simulation

Trupti Tol, QBD Team leader, Cipla Ltd

An analytical method for the determination of related substances (RS) was optimised using quality by design (QbD) approach. The selectivity issue encountered during oxidative degradation was a stumbling block, with a few poorly resolved degradant peaks (each greater than 1.0%) eluting very close to the main peak and the known impurities. Selectivity (resolution) was considered as a critical quality attribute (CQA). Buffer pH, column oven temperature, gradient slope and flow rate were the critical method variables (CMVs) studied through design of experiments (DoE). The DoE study uncovered hidden peaks and unknown criticalities, which would eventually lead to method and product failure. Since this was a sensitive case of method development it was treated accordingly, and techniques such as method of steepest ascent were adopted to attain the optimum condition. Finally, the method robustness was proved and fortified through capability analysis and Monte Carlo simulations.