A simple and isocratic HPLC method with stability indicating nature was developed and then subsequently validated for simultaneous determination of ciprofloxacin and dexamethasone in pharmaceutical formulations, human serum and urine. Best chromatographic separations were attained within run time of 10 minutes using C8 as stationary phase and mixture of phosphate buffer and methanol (41:59 v/v) as mobile phase. The mobile phase was flowed at 1.5 mL min -1 with detection of both the analytes at 270 nm using photodiode array detector. Validation of the method was accomplished using specificity, linearity, accuracy, precision, robustness, LOD and LOQ. The method was found linear from 3-21 mg mL -1 for ciprofloxacin (r 2 ≥ 0.999) and 1-7 mg mL -1 for dexamethasone (r 2 ≥ 0.999). The %age recoveries of ciprofloxacin in spiked human urine and serum were ≥99% and ≥85% respectively, while for dexamethasone they were ≥97% in both matrices. The method proficiently separated the peaks of ciprofloxacin and dexamethasone from all types of interfering substances including degradation products/impurities with purity index ≥ 0.9998. The method thus was stability-indicating and can be employed for simultaneous analysis of ciprofloxacin and dexamethasone in complex matrices involving multiple components in the mixture.
1-INTRODUCTION
Ciprofloxacin(1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-quinoline-3-carboxylic acid), a well-known antibiotic, is used to relieve bacterial infections of the eyes, corneal ulcers along with some common bacterial attacks. Dexamethasone (8S,9R,10S,11S,13S,14S,1 6R,17R)-9-Fluoro-11,17-dihydroxy-17-(2-hydroxyacetyl)-10, 13,16-trimethyl-,7,8,9,10,11,12,13,14,15,16,17-dodecahydro-3H-cyclopenta[a] phenanthren-3-one [ Figure 1] also the enforcement agencies in general to monitor the quality of the marketed products.
2-EXPERIMENTAL
Chemicals and ReagentsCiprofloxacin (99.87%) and dexamethasone (99.96%) reference standards were received from Schazoo Zaka Laboratories (Lahore, Pakistan) and were used as such without further refinement. Commercial products (Zoxan D and Ciprodex) containing 3 mg mL -1 ciprofloxacin and 1 mg mL -1 dexamethasone were analyzed during the current research work. All the chemicals used were of either HPLC grade or highest grade available commercially and were used as such. Double distilled water, other liquids used in mobile phase and all the injecting solutions were subject to filtration employing 0.45 mm nylon filters (Millipore, USA).
Equipment and Chromatographic ConditionsAll the chromatographic work was conducted on LC-20A system (Shimadzu, Japan) using PDA detector at 270 nm. Each time 20 mL volume of analytes were injected using the fixed loop and peak areas of ciprofloxacin and dexamethasone were integrated using system built software. For separation, Hypersil BDS C8 column (250 X 4.6 mm, 5 mm) was used at room temperature. Pre-mixed mobile phase was used which was prepared by mixing 59:41 v/v ratio of methanol and 0.018M phosphate buffer (pH 3.0) and was flowe...