Determination of the R-enantiomer of valsartan in pharmaceutical formulation by capillary electrophoresis.

Capillary zone electrophoresis was successfully applied to the enantiomeric purity determination of valsartan using acetyl-β-cyclodextrin (A-β-CD) as a chiral selector. Separations were carried out in a 50 µm, 64/56 cm fused-silica capillary. The optimized conditions included 25 mM phosphate buffer, pH 8.0, containing 10 mM A-β-CD as background electrolyte, an applied voltage of +30 kV and a temperature of 30 °C. Ibuprofen was used as an internal standard. The assay was validated for the R-enantiomer of valsartan in the range of 0.05-3.0%. The limit of detection was 0.01%, the limit of quantitation was 0.05%, relative to a concentration of valsartan of 1 mg/ml. Intra-day precision varied between 2.57 and 5.60%. Relative standard deviations of inter-day precision ranged between 4.46 and 6.76% for peak area ratio. The percentage recovery of the R-enantiomer of valsartan ranged between 97.0 and 99.6% in valsartan product. The assay was applied to the determination of the chiral purity of valsartan tablets and R-enantiomer of valsartan was found as an impurity.