Abstract
Two simple and sensitive spectrofluorimetric methods for the determination of lixivaptan in spiked human plasma and urine were developed. Method (A) is depend on measuring the fluorescence intensity of lixivaptan at 307/273nm in aqueous solution at pH3 using phosphate buffer, whereas method (B) is based on measuring the fluorescence spectrum of the hydrolysis product of lixivaptan after leaving it for approximately 24h at 25°C. The hydrolysis product was measured in phosphate buffer of pH11. The fluorometric determination was performed at 483/280nm. Optimization of the factors affecting on the fluorescence process of lixivaptan including the pH, diluting solvent and temperature were studied. The factors affecting the fluorescence intensity in case of the hydrolysis products was intensively studied using Box–Behnken design and optimized. The calibration curves were in the range of 57.9–500 and 50.1–400ngmL−1 for method (A) and (B), respectively. The analytical procedures were validated according to the ICH guidelines for validation. The limits of detection and limits of quantification of methods (A) and (B) were 19.11 and 16.56ngmL−1 and 57.9 and 50.17ngmL−1, respectively. The developed methods were successfully applied for determination of lixivaptan using a back calculation formula in aqueous solution (100.90±0.91%), spiked plasma (97.97±2.36%), and urine (97.59±0.87%). The developed methods could be applied in pharmacokinetic studies.
•Two spectrofluorimetric methods for lixivaptan and its hydrolysis product were developed.•Lixivaptan exhibits fluorescence at 307/273 whereas its hydrolysis products at 483/280nm.•The optimization factors affecting fluorescence intensity was carried out using Box-Behnken design.•Validation of the proposed methods according to ICH guidelines was carried out.•Analysis of the investigated drug in spiking human plasma and urine were performed.