High performance liquid chromatographic assay of a new fluoroquinolone, LB20304, in the plasma of rats and dogs

High-performance liquid chromatographic method was developed for the determination of LB 20304 (compound 1) in the plasma of rats and dogs. The analyte was deproteinized with 1 volume of methanol and 1/2 volume of 10% zinc sulfate, and the supernatant was injected onto a reversed-phase HPLC column. The mobile phase was a mixture of 24 parts of a-cetonitrile and 76 parts of 0.1% trifluoroacetic acid. The flow rate was 1 ml/min, and the effluent was monitored by fluorescence detector at an excitation wavelength of 337 nm and an emission wavelength of 460 nm. The retention time of compound 1 was 6.3 min. The assay of compound 1 was linear over the concentration range of 0.2-100 μg/ml in the plasma of rats and dogs. The lower limit of quantification was 0.2 μg/ml using 100 μl of plasma with a 97-99% accuracy and a 12-14% precision. In the 0.5, 5, and 50 μg/ml; quality control samples, the intra- and inter-day accuracy were 88-95% and 88-97%, whereas intra- and inter-day precision were 0.5-6.6% and 0.2-9.3%, respectively, in the plasma of rats and dogs. The recoveries were 68-71% independent of concentration and species in the plasma. No interferences from endogenous substances were observed. Taken together, the above HPLC assay method by deproteinization and fluorescence detection was suitable for the determination of compound 1 in the preclinical pharmacokinetics.