Two simple and sensitive high performance liquid chromatographic (HPLC) methods have been developed for the simultaneous determination of three different quinolones: enrofloxacin, lomefloxacin and ofloxacin in their pure and dosage forms, one with reversed phase HPLC and the other with ion-pair HPLC. In reversed phase HPLC, method (A), the mobile phase consists of 2.18% aqueous solution of KH2PO4 with pH adjusted to 2.4±0.2 with acetonitrile (80:20; v/v), the mobile phase pumped at flow rate of 1.2mlmin−1. A Neucleosil C18 column (10μm, 100Å), 250mm length×4.6mm diameter was utilized as stationary phase. Detection was affected spectrophotometrically at 294nm. While in ion-pair HPLC, method (B), the mobile phase was aqueous solution of 0.65% sodium perchlorate and 0.31% ammonium acetate adjusted to pH 2.2±0.2 with orthophosphoric acid: acetonitrile (81:19; v/v), the mobile phase pumped at flow rate of 1.5mlmin−1. A μ bondapack C18 column (10μm, 100Å), 250mm length×4.6mm diameter was utilized as stationary phase. Detection was affected spectrophotometrically at 294nm. Linearity ranges for enrofloxacin, lomefloxacin and ofloxacin were 4.0–108, 7.0–112 and 8.0–113μgml−1, respectively using method A and 8.0–112, 7.0–112 and 5.0–105μgml−1, respectively applying method B. Minimum detection limits obtained were 0.013, 0.023 and 0.035μgml−1 for enrofloxacin, lomefloxacin and ofloxacin, respectively using method A, and 0.028, 0.023 and 0.011μgml−1 using method B. The proposed methods were further applied to the analysis of enrofloxacin in injection and tablets containing the ofloxacin and lomefloxacin drugs, and the results were satisfied.
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