Development and validation of a combined potency assay and enantiomeric purity method for a chiral pharmaceutical compound using capillary electrophoresis

摘要

A single capillary electrophoresis method was developed for both quantitative assay and determination of enantiomeric impurity in a pharmaceutical compound. The method uses a borate buffer containing β-cyclodextrirr, and makes use of an internal standard for improved peak area precision. The quantitative assay uses a calibration curve from 50-150% of the nominal concentration, while the level of undesired enantiomer is determined by a comparison to an external limit test standard. The effects of runbuffer pH and concentration, cyclodextrin type and concentration, capillary length, and detector type (diode array or UV filter) were investigated. Validation of the method included parameters of selectivity, linearity, limit of quantitation, robustness, and migration time and quantitation precision. The precision for the main component assay is approximately 1% R.S.D. In addition, the method is capable of determining 0.5% of the minor enantiomer in the presence of the major enantiomer. The CE method and an existing HPLC method for the same compound were compared and found to give similar results.