Spectrophotometric and spectrofluorimetric determination of oseltamivir phosphate using 4-chloro-7-nitrobenzo-2-oxa 1,3-diazoleAuthor(s): Marianne Nebsen, Soheir A.A.Fattah, Dina W.Hassan, Nadia F.Youssef
Two simple and sensitive methods were introduced and validated for the determination of oseltamivir phosphate. These methods allowed quantification of oseltamivir phosphate bymonitoring its reaction with 4-chloro-7- nitrobenzo-2-oxa-1, 3-diazole (NBD-Cl) in bufferedmedium(pH9), either by recording absorbance of the final reaction product at a wavelength of 468 nm or by measuring its fluorescence emission intensity at 535 nm using an excitation wavelength of 480 nm. Different factors affecting the reaction were optimized. Linear relationships with good correlation coefficients (0.9999Â0.9997) were found between the absorbance, fluorescence intensity and the concentrations of oseltamivir phosphate in the range of 4Â24 and 0.8Â12 ïg.mL-1 for spectrophotometric and spectrofluorimetric methods, respectively. The limits of assays detection were 0.51 and 0.12 ïg.mL-1 for the first and second method, respectively. Satisfactory precisions of the methods were obtained. The proposed methods were successfully applied to the analysis of oseltamivir phosphate in pure and pharmaceutical dosage forms with good accuracy and the results were compared with those of the pharmacopeial method. The stoichiometry of the reaction was determined and the reaction pathway was postulated.