Separation of two homologous fluoroquinolone derivatives by capillary electrophoresis

Written by Simon Brigitta, Hancu Gabriel, Gyéresi Árpád

Quinolones include a number of synthetic antibacterial agents, modelled on nalidixic acid, introduced in therapy in 1962 for the treatment of urinary tract infections. As a result of extensive structure-activity research, highly potent compounds with extended spectrum of activity and improved absorption and distribution properties were synthesised. These modern analogues are classified separately as fluoroquinolones, because all group members share a 6-fluoro substituent. In our experiments we studied two fluoroquinolone derivatives: ciprofloxacin and norfloxacin, compounds with similar structure and chemical properties. The aim of our study is the development of an analytical method, which allows the simultaneous separation and identification of these compounds. In order to achieve the separation, we have chosen capillary electrophoresis, a method which gains ground in the analysis of pharmaceutical substances. The buffer solution containing 25 mM sodium tetraborate, 100 mM sodium dodecyl sulfate and 100 mM boric acid permitted an efficient separation in the pH interval of 7,9–8,3, the migration order being: ciprofloxacin and norfloxacin. In order to improve the separation, we studied the influence of the applied voltage, temperature and the injection pressure and duration. The increase of the applied voltage and temperature resulted in the decrease of the migration times. The injection parameters don’t have a significant influence on the migration times. Some analytical parameters of the method have also been checked out, in order to demonstrate the reproducibility and linearity of the method.


Keywords: fluoroquinolones, ciprofloxacin, norfloxacin, capillary electrophoresis

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