Method to determine the enantiomers of ibuprofen from human urine by high-performance liquid chromatography.

By means of ethyl chloroformate, ibuprofen enantiomers were coupled to 4-methoxyaniline. The resulting amides were resolved from each other and from urinary constituents on a Pirkle column using an isocratic mobile phase with ultraviolet detection at 254 nm. Applicability of this method for the determination of inter-individual differences in urinary metabolic profiles of ibuprofen enantiomers is demonstrated. The chromatographic behavior of the corresponding amide derivatives of two ibuprofen metabolites is also described.