Effective on-line purification for cationic compounds in rat bile using a column-switching LC technique

An on-line purification method for cationic compounds and their metabolites in rat bile was investigated using a column-switching technique. 8-Hydroxyquinoline and its glucuronide were used as test compounds. Bile samples were injected directly into the system and successful on-line extraction with high purification efficiency for analytes was achieved using two-dimensional extraction LC; that is, reversed-phase chromatography followed by cation-exchange chromatography. After removal of the endogenous component by extraction LC, chromatographic separation of the target analyte was performed on an analytical ODS column, followed by identification using UV detection. The quantitative ability of the method was evaluated on the basis of injection repeatability, linearity and accuracy. This novel method was also applied to LC/MS analysis in order to characterise the pharmacokinetics of propranolol in rats, and the metabolites were successfully identified.