Reversed-Phase Ion-Pair HPLC and TLC-Densitometric Methods for the Simultaneous Determination of Ciprofloxacin Hydrochloride and Metronidazole in Tablets

Two methods are described for the simultaneous determination of ciprofloxacin HCl (CIP) and metronidazole (MET) in binary mixture. The first method was based on the ion-pair liquid chromatographic separation of the two drugs on reversed-phase, mu Bondapak C(18) column (250 mm x 4.6 mm, 10 mu m) Waters. The mobile phase consisted of monobasic potassium phosphate (50 mM, pH 3, adjusted with phosphoric acid) and acetonitrile (65:35, v/v) containing sodium octane sulphonate (50 mM). Flow rate of 1.2 mL min(-1) was applied. Quantitation was achieved with UV detection at 280 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 3-180 and 15-180 mu g mL(-1) for CIP and MET, respectively. The second method was based on the TLC separation of the two drugs followed by densitometric measurements of their bands at 280 nm. The separation was carried out on silica gel 60 F(254) plates, using acetonitrile, ammonia, methanol, methylene chloride and hexane (1.3:1.1:2.0:3.0:1.0, v/v) as developing system. The linear regression analysis data were used for the regression line in the range of 1.5-10 mu g band(-1) for CIP and MET. The two proposed methods were successfully applied to the determination of both drugs in laboratory prepared mixtures and in commercial tablets. The optimized methods proved to be specific, robust and accurate for the quality control of the cited drugs in pharmaceutical preparation.