SIMULTANEOUS DETERMINATION OF IBUPROXAM AND IBUPROFEN IN HUMAN PLASMA BY HPLC WITH COLUMN-SWITCHING

A new high-performance liquid chromatographic method with column switching has been developed for the simultaneous determination of Ibuproxam and its metabolite Ibuprofen in plasma. The plasma samples were injected onto a LiChrosorb RP-8 precolumn after dilution with an internal standard solution in phosphoric acid. Polar plasma components were eluted with 0.05 M phosphoric acid. After valve switching, the concentrated drugs were eluted in the back-flush mode and separated on an Inertsil ODS-2 column with acetonitrile-methanol-phosphate buffer as mobile phase. The method showed excellent precision, accuracy and speed with detection limit of 0.1 mug ml-1. Total analysis time per sample was less than 30 min and the coefficients of variation for intra and inter-assay were less than 3.5 %. This method has been successfully applied to plasma samples from human volunteers after oral administration of Ibuproxam.