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. Plas ma sample preparation was carried out by adding phosphate buffer (pH 7.4, 0 .1 M), followed by extraction with trichloromethane. ENR, CIP and the inter nal standard, sarafloxacin (SAR), were separated on a reversed-phase column , and eluted with aqueous acetonitrile (80:20). The fluorescence of the col umn effluent was monitorized at lambda(ex) 338 and lambda(em) 425 nm. The r etention times were 2.28, 3.30 and 4.40 min for CIP, ENR and SAR, respectiv ely. The detection limit for the two compounds was 10 ng/mL. Standard curve s 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 (C) 1999 John Wile y & Sons, Ltd.