Highly sensitive spectrofluorimetric determination of ephedrine hydrochloride in pharmaceutical preparations

A sensitive and specific spectrofluorimetry method was developed and validated for the quantification of ephedrine (EP) in pharmaceutical preparations. The method is based on the fluorescent enhancing reaction of EP with 7-chloro-4-nitrobenzofurazan (NBD-C1; derivatization reagent), in borate buffer of pH 9 to yield a yellow, fluorescent product. Under these experimental conditions, the derivatized product of EP had excitation and emission wavelength maxima at 458 and 516 nm, respectively. The linear range of this method was 20-2500 ng/mL. The detection limit was 7.3 ng/mL EP. Intra- and interday precisions of the assay at 3 concentrations within this range were 0.037-1.77%. The low relative standard deviation values indicate good precision, and high recovery values indicate excellent accuracy of the method. The proposed method was applied to the determination of the examined drugs in pharmaceutical formulations, and the results indicate that the method is equally as accurate, precise, and reproducible as the official method.