High performance capillary electrophoresis method for determination of ibuprofen enantiomers in human serum and urine

A direct and stereospecific capillary zone electrophoresis (CZE) method for quantification ibuprofen enantiomers in biological matrices: human serum and urine, has been developed. Chiral separation of the enantiomers of ibuprofen and (+)-S-indobufen [(+)-S-INDB, internal standard, IS] was obtained in an uncoated silica capillary filled with a background electrolyte (BGE), consisted of heptakis 2,3,6-tri-O-methyl-β-cyclodextrin (TM-β-CD) in buffer of pH 5.0. The complete enantioselective analysis of ibuprofen and its 1-hydroxy metabolite confirmed appropriate specificity of the method. The electrophoretic parameters: electroosmotic (μ_EOF) and electrophoretic (μ_ep) mobility and resolution factor (R_s) were determined. Extraction procedures with organic solvent and solid phase extraction (SPE) with C₁₈ stationary phase for isolation of enantiomers from biological fluids were compared. SPE method for further studies was chosen. Stereoselective extraction of IBP enantiomers from serum at basic pH has been discovered. Validation of the method was carried out. Calibration curves of ibuprofen enantiomers were linear in the range of 0.1-25.0 μg/ml in serum and of 0.5-250.0 μg/ml in urine. Recovery of both enantiomers from serum and urine amounted 74-86 and 90-98%, respectively. Intra- and inter-day measurement precision and accuracy were below 15%. Limits of detection for IBP enantiomers amounted 0.05 and 0.25 μg/ml in samples of serum and urine, respectively. Limit of quantitation was also estimated. IBP enantiomers proved to be stable following three freeze and thaw cycles and during storage in autosampler at ambient temperature. The validated methods enable pharmacokinetic studies of enantiomers in both media. The elaborated HPCE method can be alternative to HPLC.