Isomodal column switching high-performance liquid chromatographic technique for the analysis of ciglitazone and its metabolites in human serum.

The application of isomodal column switching high-performance liquid chromatography as an alternative to gradient elution was investigated for the analysis of ciglitazone , a potential oral antidiabetic agent, and its monohydroxyl metabolites in human serum. A high-performance liquid chromatographic apparatus was designed to perform on-line fractionation of the serum extract into non-polar (drug) and polar (metabolite) fractions which were then automatically routed into individually optimized, isocratic, reversed-phase high-performance liquid chromatographic systems for simultaneous analysis. Sample fractionation was performed with a reversed-phase guard column, and solvent routing was accomplished with microprocessor-controlled switching valves. Serum was extracted for analysis by a one-step mode sequencing procedure using disposable bonded-phase columns, and quantitation was accomplished with spiked serum standards. Performance specifications of the method were defined for precision, accuracy, linearity, and sensitivity. The column switching method was found to be both expedient and reliable, and it may have general utility for the routine, quantitative analysis of drug/metabolite mixtures that cannot be assayed by simple isocratic elution methods.