Comparison of static and dynamic mode in the electrochemical oxidation of fesoterodine with the use of experimental design approach.

Electrochemical conversion of fesoterodine to one of its oxidation products was evaluated with the application of the wall-jet flow cell. A traditional, "static" mode of electrolysis was compared with the "dynamic" mode of cell performance. For statistical assessment of the data, experiments were planned and performed with the application of design of experiments approach, namely Taguchi L18 design. After screening phase, the experimental settings were broadened or adjusted according to the results and optimization was performed. All of the samples were electrolysed with the use of chronoamperometric method in a three electrode system. The electrolysed samples were analysed using UHPLC-PDA-QDA method. The chromatographic run was performed in gradient elution with the application of C8 column. The response was expressed as % area of the main peak found with the PDA detection method whereas QDA detector was used in positive SIM mode for structural confirmation. All data obtained for both screening and optimization were treated together and linear models were adjusted. The use of large-surface glassy carbon electrode along with pH~7 were found to be the most significant factors influencing electrochemical oxidation of fesoterodine in both modes. The major differences were identified in terms of voltage applied to the electrodes which yielded the highest amounts of oxidation product. Evolution of electrochemical methods may serve as complementary technique in stress degradation studies in pharmaceutical industry.