Spectrofluorimetric determination of brexpiprazole <i>via</i> quenching of erythrosine B fluorescence: optimization using Box–Behnken design

A simple, rapid and sensitive spectrofluorimetric method was developed and validated for the determination of brexpiprazole in bulk, pharmaceutical formulations and spiked human plasma. The method is based on the fluorescence quenching of erythrosine B upon its reaction with brexpiprazole in Toerell-Stenhagen buffer solution (pH 3.2). A Box-Behnken design was employed to optimize the factors influencing the method's performance considering factors such as buffer pH, buffer and reagent volumes and reaction time. The fluorescence intensity was measured at 554 nm after excitation at 530 nm. The method exhibited a linear response over the concentration range of 0.2-2 μg mL^-1. The limit of detection and limit of quantitation were found to be 0.0515 and 0.1561 μg mL^-1, respectively. The method was validated according to ICH guidelines, demonstrating good accuracy, precision and robustness. The proposed method was successfully applied to determine brexpiprazole in commercial tablets and spiked human plasma samples with excellent recoveries. The results obtained were statistically compared with those of a reference method showing no significant difference. This cost-effective and efficient method offers a valuable tool for routine quality control analysis of brexpiprazole in pharmaceutical formulations and biological samples.