Determination of trace enantiomeric impurities in chiral compounds by capillary electrophoresis with uncoated, cationic, anionic and neutral surface modified capillaries

The usefulness of commercially available polyamine, sulphonic acid and neutral coated capillaries is demonstrated for the resolution of chiral drugs. The methods, using cyclodextrins and their derivatives are developed from conventional fused-silica capillary procedures without any changes to the procedures. Different coatings can be used to adjust the order of elution of enantiomers when one of the enantiomers is present as a trace level impurity. Limit of quantitation levels of <0.1% (m/m) have been illustrated for D- or L-tryptophan in the presence of the other enantiomer with acceptable levels of reproducibility. Similar levels have been detected for warfarin and propranolol, using a polyamine-coated capillary, The coated capillaries were stable to long-term changes in the electrolyte and its pH value and the methods were interchangeable with capillaries obtained from different batches. (C) 1998 Elsevier Science B.V. All rights reserved.