Simultaneous determination of enrofloxacin and its primary metabolite, ciprofloxacin, in plasma by HPLC with fluorescence detection.

A simple and sensitive HPLC method has been developed for the simultaneous determination of enrofloxacin (ENR) and ciprofloxacin (CIP) in plasma. Plasma sample preparation was carried out by adding phosphate buffer (pH 7.4, 0.1 M), followed by extraction with trichloromethane. ENR, CIP and the internal standard, sarafloxacin (SAR), were separated on a reversed-phase column, and eluted with aqueous acetonitrile (80:20). The fluorescence of the column effluent was monitorized at lambda(ex) 338 and lambda(em) 425 nm. The retention times were 2.28, 3.30 and 4.40 min for CIP, ENR and SAR, respectively. The detection limit for the two compounds was 10 ng/mL. Standard curves were linearly related to concentration in the range from 1 to 1500 ng/mL. The recovery was 93% for ENR and 75% for CIP. Copyright 1999 John Wiley & Sons, Ltd.