Determination of enantiomeric excess by capillary electrophoresis

Capillary electrophoresis (CE) is becoming an established method for the de termination of chiral trace impurities. This paper provides an overview of the state of the art of CE for such determinations. Detection limits of 0.1 % impurity is widely accepted as a minimum requirement for chiral trace imp urity determinations. This can be relatively easily achieved with CE. Howev er, determination of lower concentrations requires careful optimization of the separation system. Four factors that are of particular significance for trace enantiomeric determinations: resolution, limit of detection, linear range and type of detection, are discussed. Further, the advantages and dis advantages of derivatization in this context are treated as well as the sep aration approach, i.e., direct chiral separation or separation after the fo rmation of diastereomers. It is concluded that the limit of impurity detect ion can be about 0.05% when UV detection is employed. Using laser-induced f luorescence detection, a quantitative determination at the 0.005% level is often possible.