Simultaneous determination of losartan and active metabolite EXP3174 in rat plasma by HPLC with column switching

A new liquid chromatographic method with column-switching has been developed for the simultaneous determination of losartan and its active metabolite, EXP3174 in rat plasma. The plasma sample was injected onto a precolumn of LiChroprep RP-8 after dilution with 5% acetonitrile in 50 mM phosphoric acid. Polar plasma components were eluted using this diluent. After valve switching, the concentrated drugs were eluted in the back-flush mode and separated by an Inertsil ODS-2 column with acetonitrile-acetate buffer. The method showed excellent precision, accuracy and speed with detection limit 20 ng mL(-1). Total analysis time per sample was less than 40 min and the coefficients of variation for intra and inter-assay were 4.8%. This method has been successfully applied after oral administration of losartan to rat plasma samples.