Analytical Quality by Design-compliant development of a cyclodextrin-modified micellar electrokinetic chromatography method for the determination of trimecaine and its impurities

March 2022, the International Council for Harmonization released two draft guidelines (ICH Q14 and ICH Q2(R2)), with the aim of specifying the development and validation activities that should be carried out during the lifespan of an analytical technique used to assess the quality of drug substances and medicinal products. These new guidelines highlight the importance of a comprehensive strategy in method development involving multivariate approach and risk assessment. In this study, these new prospects were applied in Capillary Electrophoresis (CE) method development for the purity control of the drug product containing the local anaesthetic and cardiac antiarrhythmic drug trimecaine (TMC). The enhanced approach of Analytical Quality by Design was applied, following a well-defined framework, from the definition of Analytical Target Profile (ATP) to the identification of Method Operable Design Region (MODR). According to the ATP, the CE procedure should be able to simultaneously and accurately quantify TMC and its four related impurities in the drug product, with a quantitation limit for the impurities equal or lower to 0.1% with respect to drug substance, and in a short analysis time. Method scouting phase was addressed to collect preliminary knowledge on the separation system, taking into consideration several pseudostationary phases, including different surfactants and various cyclodextrins, and further tuning the background electrolyte by organic modifiers. The selected operative mode was a Micellar ElectroKinetic Chromatography system made by sodium dodecyl sulfate micelles with the addition of dimethyl-β-cyclodextrin in phosphate-borate buffer. After performing risk assessment by means of Ishikawa Diagram, the knowledge space was investigated through a screening matrix taking into consideration critical method parameters involving the composition of the background electrolyte and the instrumental settings. The critical method attributes were identified as analysis time and critical resolution values. On the basis of the screening results, the next optimization steps will involve Response Surface Methodology and Monte Carlo simulations for the definition of the MODR.