OPTIMIZATION OF A CAPILLARY ELECTROPHORESIS METHOD TO DETERMINE THE CHIRAL PURITY OF A DRUG

Capillary electrophoresis (CE) using hydroxypropyl-beta-cyclodextrin ( HP-beta-CD) in the separation buffer was investigated to determine the overall chiral purity of a drug containing a single stereogenic cente r. The effects of primary factors -pH, buffer components, buffer conce ntration, cyclodextrin concentration and sample amount (concentration and injection volume)- on the resolution of the enantiomers were inves tigated. Secondary factors such as the HP-beta-CD source, lot and degr ee of substitution that were expected to affect the robustness of the assay were investigated also. The linearity, quantitation limit for th e trace enantiomer and the precision of the measurements were determin ed. This study shows that understanding and optimizing the assay condi tions leads to a chiral CE separation that is comparable to that obtai ned by chiral HPLC. However, chiral CE separations achieved with buffe r additives have the advantages of shorter run times, higher numbers o f theoretical plates (greater resolution), smaller amounts of chiral a dditive (less cost) and greater ruggedness (separation virtually indep endent of column properties unlike HPLC).