First-derivative synchronous spectrofluorimetric method for simultaneous determination of dapagliflozin and sitagliptin in dosage forms and spiked human plasma

The co-administration of Dapagliflozin and Sitagliptin has attracted considerable interest in the management of type 2 diabetes mellitus due to their complementary therapeutic effects. However, their simultaneous determination is analytically challenging because of the significant overlap in their native fluorescence spectra. In this study, a selective and sensitive first-derivative synchronous spectrofluorimetric method was developed for the simultaneous determination of both drugs without prior separation. The proposed approach enabled efficient spectral resolution through zero-crossing points at 348 nm and 289 nm for dapagliflozin and sitagliptin, respectively, using a constant wavelength difference (Δλ = 30 nm). The method exhibited excellent linearity over the concentration ranges of 50-1000 ng/mL and 100-2000 ng/mL for dapagliflozin and sitagliptin, respectively, covering concentration levels relevant to their reported maximum plasma concentrations (Cmax), with low limits of detection (16.02 and 31.07 ng/mL, respectively), indicating high sensitivity. The proposed method demonstrated satisfactory accuracy (mean recoveries of 100.67% and 99.86%) and precision (%RSD < 2%). The method was successfully applied to the analysis of pharmaceutical dosage forms and spiked human plasma, showing reliable recoveries. To the best of our knowledge, this is the first validated spectrofluorimetric method for the simultaneous determination of these co-administered drugs, offering a simple, cost-effective, and efficient alternative to conventional analytical techniques.