DETERMINATION OF TICARCILLIN EPIMERS IN PLASMA AND URINE WITH HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A high-performance liquid chromatographic method was developed for det ermining the concentrations of ticarcillin (TIPC) epimers in human pla sma and urine. Samples were prepared for HPLC analysis with a solid-ph ase extraction method and the concentrations of TIPC epimers were dete rmined using reversed-phase HPLC. The mobile phase was a mixture of 0. 005 M phosphate buffer (pH 7.0) and methanol (12:1, v/v) with a flow-r ate of 1.0 ml/min. TIPC epimers were detected at 254 nm. Baseline sepa ration of the two epimers was observed for both plasma and urine sampl es with a detection limit of ca. 1 mu g/ml with a S/N ratio of 3. No p eaks interfering with either of the TIPC epimers were observed on the HPLC chromatograms for blank plasma and urine. The recovery was more t han 80% for both plasma and wine samples. C.V. values for intra- and i nter-day variabilities were 0.9-2.1 and 1.1-6.4%, respectively, at con centrations ranging between 5 and 200 mu g/ml. The present method was used to determine the concentrations of TIPC epimers in plasma and uri ne following intravenous injection of TIPC to a human volunteer. It wa s found that both epimers were actively secreted into urine and that t he secretion of TIPC was not stereoselective. Plasma protein binding w as also measured, which revealed stereoselective binding of TIPC in hu man plasma.