Enantioseparation of 3,4-dihydroxyphenylalanine and 2-hydrazino-2-methyl-3-(3,4-dihydroxyphenyl)propanoic acid by capillary electrophoresis using cyclodextrins

The enantiomeric separations of 3,4-dihydroxyphenylalanine (dopa) and 2-hyd razino-2-methyl-3-(3,4-dihydroxyphenyl)propanoic acid (carbidopa) by capill ary electrophoresis were studied using several native, neutral and anionic cyclodextrins as chiral additives and uncoated fused-silica capillaries. Th e effect of the type and concentration of the cyclodextrin added to 20 mM p hosphate buffer (pH 2.5) on enantioseparation and migration times was studi ed. A high resolution value of 15.63 was obtained for dopa enantiomers with a buffer containing 20 mM single isomer, heptakis(2,3-diacetyl-6-sulfato)- beta-cyclodextrin. The enantiomers of carbidopa were separated using 20 mM carboxymethyl-beta-cyclodextrin as a chiral resolving agent. Both methods a llowed the determination of 0.1% of the D-enantiomer (second migrating) in the presence of the L-enantiomer (first migrating) of dopa and carbidopa wi th a good precision. These methods also gave good results in terms of preci sion for both peak area, migration time, linearity and accuracy. (C) 2000 P ublished by Elsevier Science B.V. All rights reserved.