Two different synchronous spectrofluorimetric approaches for simultaneous determination of febuxostat and ibuprofen

Two green, simple and sensitive synchronous spectrofluorimetric methods were developed for the first time for the simultaneous estimation of febuxostat (FEB) and ibuprofen (IBU). Method I is constant-wavelength synchronous spectrofluorimetry where FEB and IBU were recorded at 329 and 258 nm, respectively, using Δλ of 40 nm. Method II is constant-energy synchronous spectrofluorimetry using a wavenumber interval of -4000 cm^-1. All measurements were carried out in a borate buffer of pH 7 and distilled water for dilution which increased the methods' greenness. The two methods were rectilinear over concentration ranges of 30.0-700.0 ng ml^-1 and 0.5-9.0 µg ml^-1 in the first method and 20.0-500.0 ng ml^-1 and 0.1-8.0 µg ml^-1 in the second method for FEB and IBU, respectively. High sensitivity was attained for the two drugs with limits of quantitations (LODs) down to 0.41 and 5.51 ng ml^-1 in the first method and 0.25 and 3.32 ng ml^-1 in the second method for FEB and IBU, respectively. Recovery percentages were in the range of 97.3-101.9% after extraction from spiked human plasma samples, demonstrating high bioanalytical applicability. The two methods were further applied to tablet dosage forms with good recovery results. The methods' greenness was assessed according to the analytical Eco-Scale and Green Analytical Procedure Index guidelines.