Liquid chromatographic determination and plasma concentration profile of optical isomers of ibuprofen in humans.

A sensitive and specific high-performance liquid chromatographic assay for the optical isomers of ibuprofen in plasma is reported. The isomers were converted to their diastereoisomeric S(+)-2-octyl esters and were resolved with two silica columns in series and a mobile phase containing 0.05% isopropyl alcohol in heptane. The lower limit of sensitivity was 0.5 micrograms/mL. The plasma concentrations of the optical isomers in a normal volunteer following administration of racemic, S(+)-, and R(-)-ibuprofen are reported. Following administration of R(-)-ibuprofen, there was stereoselective inversion of R(-)- to S(+)-ibuprofen.