Determination of the antibacterial drug enrofloxacin by solid-phase spectrofluorimetry

A method for the determination of trace amounts of enrofloxacin based on solid-phase spectrofluorimetry has been developed. The relative fluorescence intensity of enrofloxacin fixed on Sephadex SP C-25 gel was measured directly after packing the gel beads in a 1-mm silica cell, using a solid-phase attachment. The wavelengths of excitation and emission were 277 and 448 nm, respectively. The linear concentration range of application was 0.2-4.0 ng mL(-1) of enrofloxacin, with a relative standard deviation of 1.2% (for a level of 2.0 ng mL(-1)) and a detection limit of 0.04 ng mL(-1). The method was applied to the determination of enrofloxacin in commercial pharmaceutical formulations and spiked canine serum samples. It was validated using HPLC as a reference method and applying the standard addition methodology. Recovery levels of the method reached 100% in all cases.