Highly sensitive synchronous fluorescence measurement of danofloxacin in pharmaceutical and milk samples using aluminium (III) enhanced fluorescence

A simple, rapid and sensitive constant wavelength synchronous fluorescence method is developed for the determination of danofloxacin (DAN) in pharmaceutical formulations and its residue in milk based on Al(III) enhanced fluorescence. The synchronous fluorescence intensity of the system is measured at 435 nm using ∆ λ = 80 nm and an excitation wavelength of 280 nm. A good linear relationship between enhanced fluorescence intensity and DAN concentration is obtained in the range of 3-100 ng mL(-1)(r (2) = 0.9991). The limit of detection (LOD, S/N = 3) of the present method is 0.9 ng mL(-1). The proposed method can be successfully applied to the determination of DAN in pharmaceutical formulations and in milk without serious interferences from common excipients, metal ions and other co-existing substances. The method can be used as a rapid screening to judge whether the DAN residues in milk exceed Maximum Residue Limits (MRLs) or not.