Quality-by-Design Steered Development and Validation of Analytical Method for the Estimation of Etodolac: Integration of Monte Carlo Simulations and Green Analytical Principles

The present study aimed to develop and validate a robust, eco-friendly, and regulatory-compliant reversed-phase high-performance liquid chromatography (RP-HPLC) method for the quantitative estimation of etodolac in niosomal gel-based pharmaceutical formulations. The method was systematically developed using an Analytical Quality by Design (AQbD) framework, integrating chemometric and statistical tools in accordance with ICH Q8, Q9, Q10 and Q14 guidelines. The Principal Component Analysis (PCA) was employed to select an optimal analytical wavelength, identifying 279 nm as a stable and noise-free detection wavelength. Quality Risk Management tools, including Ishikawa analysis and a risk assessment matrix, were used to identify critical method parameters, which were further screened using a Taguchi design and optimized through Central Composite Design-based Response Surface Methodology. The flow rate and mobile phase composition were identified as the most influential variables affecting critical analytical attributes such as peak area, retention time, tailing factor, and theoretical plate count. The optimized chromatographic conditions utilized a C18 column with an acetonitrile–ammonium acetate buffer (pH 3.0) at a flow rate of 1.0 mL min⁻¹. The Method Operable Design Region (MODR) was validated using Monte Carlo simulation (50,000 iterations), confirming the robustness and reliability of the method. The method was validated according to ICH Q2(R2) guidelines and demonstrated excellent linearity (r² = 0.99989) over the concentration range of 0.1–10 µg/mL, high accuracy (99.83–101.08%), precision (%RSD < 2%), and sensitivity (LOD 0.03 µg/mL, LOQ 0.1 µg/mL), with robustness studies confirming negligible impact of deliberate variations. The developed method also exhibited excellent environmental sustainability with an Analytical Eco-Scale score of 80, along with high practical applicability reflected by a BAGI score of 82.5 and an overall whiteness score of 82.5. Furthermore, the developed analytical method was utilized to estimate the amount of etodolac present in the niosomal based formulation. The etodolac-loaded niosomes were successfully formulated and incorporated into a gel system, demonstrating high entrapment efficiency (96.72%) and a sustained drug release profile compared to conventional niosomes. Overall, the proposed AQbD-based analytical strategy provides a scientifically rigorous, lifecycle-oriented approach suitable for routine quality control, stability studies, and regulatory applications of etodolac in advanced pharmaceutical formulations.