Second-derivative synchronous fluorimetry and time-programmed HPLC-fluorescence detection for simultaneous estimation...

Diabetes Mellitus is directly related to female anaphrodesia. Female Viagra or Flibanserin (FLB), U.S. FDA approved in 2015, is specifically indicated for premenopausal Hypoactive Sexual Desire Disorder, HSDD, which is one of the primary consequences of Diabetes Mellitus. Simultaneous analysis of the concomitantly administered, FLB and oral antidiabetics, as Sitagliptin phosphate (STG), is a crucial demand to investigate mutual drug-drug interaction. The latter is responsible for uncontrolled glycaemia and higher risk of sudden hypoglycemia. Two simple, sensitive, economical and direct analytical methods, namely, Second-Derivative Synchronous Fluorimetric Spectroscopy, D₂-SFS, and High Performance Liquid Chromatography with fluorimetric detection, HPLC-FD, are established for simultaneous determination of FLB and STG in their binary mixtures. First method relies on measuring D₂-SFS spectra of both drugs, at Δλ = 25 nm, along linearity ranges of 0.05-1 μg/mL for both drugs. The second method is a chromatographic one with gradient elution of FLB and STG on RP-ZORBAX Eclipse C₁₈ column (5 µm, 4.6 × 150 mm). Mobile phase; phosphate buffer: acetonitrile, pH 4.5, with a flow rate of 1 mL/min at room temperature has been used. Time programmed fluorimetric detection is optimized at λem = 305 nm for STG (0.0-5.9 min), at λem = 375 nm for FLB (6-9 min) after both excitation at λex = 257 nm, in the linear ranges of 1-40 μg/mL and 5-60 μg/mL for FLB and STG, respectively. Proposed methods have been validated according to ICH guidelines, then applied for simultaneous quantitation of FLB and STG in their laboratory-prepared mixtures and in spiked human plasma samples. Satisfactory Student's t-value and F-variance ratio have been obtained upon comparing the results of both methods.