Separation and determination of clopidogrel and its impurities by capillary electrophoresis

Clopidogrel bisulphate, an anti-platelet drug, has been separated from its impurities, namely impurity A, B and C by capillary zone electrophoresis (CZE) using uncoated fused-silica capillary (50.0 microm internal diameter, 31.2cm total length). Four factors affected the separation: buffer concentration, pH of the buffer, concentration of the chiral selector and the applied voltage. Optimization and robustness studies were performed with the aid of reduced central composite experimental design. The buffer used was triethylamine-phosphoric acid and the chosen chiral selector was sulphated beta-cyclodextrin (SCD). The best separation was achieved by using 10mM buffer, pH 2.3, containing 5% (mass/volume (m/v)) SCD. Reversed polarity mode was used with an applied voltage of -12kV and the capillary temperature was maintained at 20 degrees C. The method was validated for quantitative determination of the drug. It offered a limit of detection (LOD) of 0.13 microg/ml, a limit of quantitation (LOQ) of 0.4 microg/ml, and a linearity range of 0.4-300 microg/ml. Commercial bulk samples were analyzed using the developed method.