Quantitative determination of ofloxacin, ciprofloxacin, norfloxacin and pefloxacin in serum by high pressure liquid chromatography.

A simple sensitive HPLC method for the analysis of ciprofloxacin, norfloxacin, ofloxacin and pefloxacin in serum is described. The quinolones were extracted using dichloromethane under neutral conditions, followed by drying under nitrogen and dissolving in mobile phase before chromatographic analysis. The stationary phase consisted of a stainless steel column with Nucleosil CI8 (5 microns), and a mobile phase of 0.04 M phosphoric acid, tetrabutylammoniumiodide as ion-pairing reagent and methanol (pH 2.2). UV absorbance was used for detection. The method was shown to be linear, quantitative and reproducible in the therapeutic range of each of these quinolones. Serum levels of ofloxacin and ciprofloxacin were determined and compared to those found by a microbiological assay. Good correlation was found for the assay of ciprofloxacin as well as for ofloxacin.