Stability-Indicating Liquid Chromatography-Spectrophotometric UV Method for the Simultaneous Determination of Marbofloxacin, Dexamethasone and Clotrimazole in a Liquid Pharmaceutical Dosage Form

A novel, simple and reliable reversed-phase liquid chromatography (LC)-spectrophotometric UV stability-indicating method was developed and validated for the simultaneous assay of marbofloxacin, clotrimazole and dexamethasone acetate in the presence of their impurities and degradation products in a pharmaceutical formulation for veterinary use. A C18 (75 x 4.6 mm, 4 A mu m) column was used with an acetonitrile-ammonium acetate mixture as mobile phase delivered with gradient elution. A diode-array detection was used in the 200-400 nm range and the detection wavelength was set at 260 nm. Validation carried out on the pharmaceutical dosage form, according to Veterinary International Conference on Harmonization guidelines, demonstrated excellent specificity, linearity, precision, accuracy and robustness. Excellent specificity with respect to vehicle and degradation products obtained after forced degradation (i.e., oxidation, acid, alkaline and thermal degradation) was demonstrated. As for linearity, the LC-UV assay method is applicable in the 0.180-0.420 mg mL(-1) concentration range for marbofloxacin (r (2) = 0.99), 0.060-0.140 mg mL(-1) for dexamethasone acetate (r (2) = 0.97) and 0.600-1.400 mg mL(-1) for clotrimazole (r (2) = 0.98). Very good repeatability (RSD < 0.8 %) and inter-day precision (RSD < 2.5 %) were observed for all analytes. Accuracy was in the 93-104 %, 98-111 % and 99-108 % confidence interval (95 %) for marbofloxacin, dexamethasone acetate and clotrimazole, respectively. The variations (+/- 20 %) of mobile phase flow rate and pH, and oven column temperature did not exhibit an impact on the analyte content accuracy, demonstrating the robustness of the method. The LC-UV method here developed and validated may be used routinely for quality control.