A novel quality by design approach for development and validation of a green reversed‐phase HPLC method with fluorescence detection for the simultaneous determination of lesinurad, febuxostat, and diflunisal: Application to human plasma

Abstract A novel and eco‐friendly reversed‐phase HPLC method with fluorescence detection was developed for simultaneous estimation of two co‐administered antigout drugs (lesinurad and febuxostat) with diflunisal as a nonsteroidal anti‐inflammatory drug. Unlike routine methodology, the developed method was optimized using analytical quality by design approach. A full factorial design was applied to optimize the effect of variable factors on chromatographic responses. The chromatographic separation was performed using isocratic elution on the Hypersil BDS C18 column at 40°C. The mobile phase consisted of acetonitrile:potassium phosphate buffer (30.0 mM; pH 5.5, 32.2:67.8% v/v) pumped at a flow rate of 1.0 mL/min and injection volume of 20.0 μL was employed. The proposed method was able to separate the ternary mixture in <10 min. The calibration curves of diflunisal, lesinurad, and febuxostat were linear over concentration ranges of 50.0–500.0, 50.0–700.0, and 20.0–700.0 ng/mL, respectively. Recovery percentages ranging from 98.1 to 101.3% with % relative standard deviation of <2% were obtained upon spiking to human plasma samples, indicating high bioanalytical applicability. Furthermore, the method was found to be excellent green when it was assessed according to Green Analytical Procedure Index and analytical Eco‐Scale guidelines.