A simple isocratic high-pressure liquid chromatographic assay of quinolones in serum

A simple HPLC assay was evaluated for the analysis of tiprofloxacin, enoxacin, fieroxacin, lomefloxacin, norfloxacin, ofloxacin and pefloxacin and their available metabolites in serum. A reverse-phase column was used with an acidic mobile phase containing heptane sulphonic acid. Two reverse-phase columns of similar selectivity but different efficiencies were used. The eluate was monitored by UV or fluorescence detection. Serum was prepared for assay by protein precipitation with acids which yielded high recoveries with good reproducibility (CV < 2·5%). Absorbance maxima and optimum fluorescence detection parameters were determined for each quinolone. Assay specificity, tested by analysing serum from 20 hospital patients, was good. Analysis of patient and volunteer sera for enoxacin and fieroxacin showed good agreement with a microbiological method (regression coefficients > 0·956). A single, specific analytical method applicable to the quinolone group may be simpler and cheaper for the clinical laboratory. The assay described here provides a simple to perform, sensitive and specific method for quantitation of several quinolones and their metabolites.