Determination of ziprasidone in pharmaceutical formulations by capillary zone electrophoresis

The atypical antipsychotic drug Ziprasidone was determined by capillary zone electrophoresis in pharmaceutical formulations. Extraction of the drug from the formulation consisted in a simple dissolution step with methanol as solvent, and enables determination of the drug without any interference from the excipients. It was found that at pH of the background electrolyte above 5 the peak of the drug exhibited a tailing, at pH 6 or higher even a disappearance of the peak in the electropherogram was observed. This behaviour was related to the concomitant reduction of the solubility of the drug in the background electrolyte upon deprotonation at higher pH. As a consequence, analyses were carried out with formate buffer, pH 3.0, and enabled run times of about 3 min. The method was validated in terms of stability, specificity, precision, accuracy, linearity, quantitation limits, and robustness, and was applied to the analysis of different commercial capsules.