Abstract

Six simple, specific, accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of gatifloxacin (GFC) and dexamethasone (DEX) without preliminary separation. The first method was based on direct spectrophotometric determination of GFC at 291.6 nm as DEX shows nearly zero crossing at this wavelength. The second and third ones, used for simultaneous determination of both drugs were dual wavelength method and a first derivative method. The other methods were manipulating ratio spectra namely first derivative of the ratio spectra, ratio difference and mean centering of ratio spectra and were used for determination of DEX. Quantitation of the two studied drugs using the proposed methods was achieved in the concentration range of 1.5-17.5 and 5-50 μg/ml, respectively. The developed methods were successfully applied for the analysis of of GFC and DEX in their synthetic mixtures and pharmaceutical formulation without any interference from common excipients; recoveries ranging from 98.59- 101.78 % ± 0.44- 2.06. The results obtained were statistically compared to that of a reported method showing no significant difference regarding both accuracy and precision. The proposed methods are very simple with minimum manipulation steps, don’t need any sophisticated apparatus or a special program. The RSD for all parameters was found to be within the limits, which indicates the validity of method. Accordingly, these methods could be successfully applied for routine analysis of the studied drugs either in their pure form or combined dosage form in quality control laboratories.