DEVELOPMENT OF AN ISOCRATIC HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHOD FOR MONITORING OF CIPROFLOXACIN PHOTODEGRADATION

An isocratic reversed-phase ion-pair high-performance liquid chromatog raphic method was developed for monitoring the photodegradation of cip rofloxacin in aqueous solutions. Changes in the chromatographic behavi our of ciprofloxacin and its degradation products under the influence of organic modifiers, anionic and cationic ion-pair reagents and pH we re investigated. Baseline separation was achieved with use of an eluen t of acetonitrile-phosphoric acid (20 mM, pH 2.3) containing 2.5 mM 1- heptanesulphonic acid sodium salt. The method was applied to the quant ification of ciprofloxacin in irradiated solutions. The calibration gr aphs were linear from 5 to 150 mu g/ml (r>0.9999). Within the same ran ge, the accuracy was 99-102% of the expected values. The intra-assay r epeatability of the peak areas and retention times was good (R.S.D. le ss than or equal to 0.9%). Likewise the intra-day reproducibility of t he method was good: R.S.D. values (n = 6) were less than or equal to 2 .3% and 1.8% for the lowest and highest concentrations, respectively. The inter-day precision gave a mean R.S.D. of 2.4% for peak areas and R.S.D. of 3.3% for retention times during a working period of three mo nths.