Spectrofluorimetric determination of two β-agonist drugs in bulk and pharmaceutical dosage forms via derivatization with dansyl chloride

A sensitive, simple and rapid spectrofluorimetric method has been developed for the determination of both Fenoterol hydrobromide (FNT) and Ritodrine hydrochloride (RTH) in pure and dosage forms. The method is based on derivatization using dansyl chloride (DNS-Cl) as fluorogenic agent and measuring the fluorescence of the products at emission wavelengths of 517 and 515 nm after excitation at 348 and 343 nm for FNT and RTH, respectively. Different experimental parameters affecting the fluorescence intensities were carefully studied and optimized. The relation between fluorescence intensities and drug concentrations were rectilinear over the concentration range of 0.25–6.0 μg/mL for both drugs with a minimum detectability of 0.065 and 0.045 μg/mL for FNT and RTH, respectively. The percentage recoveries ±SD were 100.1 ± 0.9, 99.9 ± 0.6 for FNT and RTH respectively. The proposed method was successfully applied to the determination of both drugs in their commercial dosage forms. The obtained results were statistically validated and agreed well with those obtained with reference methods. A suggestion for the reaction pathway with DNS-Cl was postulated.