Enantioseparation of tartaric acid by ligand exchange CE with a Cu(II)-D-quinic acid system was studied Racemic tartaric acid was enantioseparated by ligand exchange CE using BCEs containing relatively low Cu(II)-D-quinic acid molar ratios ranging from 1 1 to 1.3 and high molar ratios ranging from 1.8 to 1 12 but was not enantioseparated using BGEs with medium molar ratios ranging from 1 4 to 1 6 While the migration order of-D-tartaric acid was prior to L-tartaric acid at the lower Cu(II)-D-quinic acid molar ratios, the enantiomer migration order was reversed at the higher molar ratios. These results were compared with those for Ni(II)-D-quinic acid system The molar ratio dependence of enantiomer migration order can be attributed to a change in the coordination structure of Cu(II) ion with D-quinic acid.