Determination of unbound 20(S)-camptothecin in rat bile by on-line microdialysis coupled to microbore liquid chromatography with fluorescence detection

To evaluate the biliary excretion of unbound camptothecin, a flow-through m icrodialysis probe was constructed for bile sampling. The shunt linear prob e was connected from the bile duct, between the liver side to the duodenum to avoid obstruction of the bile duct or bile salt waste. For automatic ana lysis of microdialysate, an on-line injector was connected to a microbore h igh-performance liquid chromatographic column with fluorescence detection. Samples were eluted with a mobile phase containing methanol-100 mM monosodi um phosphoric acid (35.65, v/v, pH 2.5, adjusted with orthophosphoric acid) . The limit of quantification was 1 ng/ml for camptothecin. Following campt othecin administration (5 mg/kg, i.v.), it was found in the bile microdialy sate. It was concluded that the in vivo microdialysis technique yields usef ul data on the biliary excretion of camptothecin. This method is suitable f or additional pharmacokinetic studies in rat bile. (C) 1999 Elsevier Scienc e B.V. All rights reserved.