Capillary Zone Electrophoresis method for determination of (+)-S clopidogrel carboxylic acid metabolite in human plasma and urine designed for biopharmaceutic studies

Fast and reproducible Capillary Zone Electrophoresis (CZE) method for the quantification of (+)-S clopidogrel carboxylic acid metabolite in human fluids was elaborated for the first time. Optimal buffer and CZE conditions were established to obtain the complete separation of clopidogrel, its metabolite and piroxicam (internal standard), during one analytical run. Finally, resolution of the analytes was obtained in an uncoated silica capillary filled with a phosphate buffer of pH 2.5. The analytes were isolated from plasma and urine samples using solid phase extraction (SPE). Validation of the CZE method was carried out. The calibration curve of clopidogrel was linear in the range of 0.5–10.0 mg/L in plasma and urine, whereas for (+)-S carboxylic acid metabolite linearity was confirmed in the range of 0.25–20.0 mg/L in plasma and 0.25–10.0 mg/L in urine. Intra- and inter-day precision and accuracy were repeatable. LOD and LOQ were also estimated. SPE recovery of the analytes from plasma and urine was comparable and greater than 80%. The validated method was successfully applied in pharmacokinetic investigations of (+)-S carboxylic acid metabolite of clopidogrel following the oral administration of clopidogrel to patients prior to percutaneous coronary intervention.