Chiral Profiling Analysis of β-Blockers by Capillary Electrophoresis Using Dual Chiral Selectors

Simultaneous analysis of several beta-blockers using a novel dual chiral selector system was achieved for their accurate chiral discrimination by chiral capillary electrophoresis (CE) in normal polarity mode. The CE system was operated using heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) dissolved in 100mM phosphoric acid-triethanolamine buffer (pH 3) and (+)- or (-)-18-crown-6-tetracarboxylic acid (18-C-6-TA) as a co-chiral selector in DM--CD solution. All eight investigated analytes were resolved using (+)-18-C-6-TA as a co-chiral selector in the presence of DM-beta-CD solution, whereas the other -blockers, except propranolol, were resolved using (-)-18-C-6-TA as the second chiral selector in DM-beta-CD solution. Also, DM-beta-CD had a major effect on chiral discrimination compared with 18-C-6-TA as a co-chiral selector. Relative migration times to that of (S)-pindolol as an internal standard were characteristic of each enantiomer with good precision. The method showed good linearity with a correlation coefficient (r >= 0.993). The precision as a percentage of relative standard deviation (% RSD) and accuracy as a percentage of relative error (% RE) ranged from 0.5 to 9.6 and from -5.7 to 9.1, respectively. These were adequate for the chiral assay of the beta-blockers investigated. Thus, the present chiral profiling method is expected to be useful for accurate chiral discrimination and optical purity tests of chiral beta-blockers and their related drugs.