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

Enantiomeric capillary electrophoresis (CE) profiles of eight racemic β‐blockers in normal polarity mode with (a) 20 mM (+)‐18‐C‐6‐TA and (b) 20 mM (−)‐18‐C‐6‐TA in 10 mM DM‐β‐CD solution as dual chiral selectors. Simultaneous analysis of several β‐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)‐β‐cyclodextrin (DM‐β‐CD) dissolved in 100 mM phosphoric acid–triethanolamine buffer (pH 3) and (+)‐ or (−)‐18‐crown‐6‐tetracarboxylic acid (18‐C‐6‐TA) as a co‐chiral selector in DM‐β‐CD solution. All eight investigated analytes were resolved using (+)‐18‐C‐6‐TA as a co‐chiral selector in the presence of DM‐β‐CD solution, whereas the other β‐blockers, except propranolol, were resolved using (−)‐18‐C‐6‐TA as the second chiral selector in DM‐β‐CD solution. Also, DM‐β‐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 β‐blockers investigated. Thus, the present chiral profiling method is expected to be useful for accurate chiral discrimination and optical purity tests of chiral β‐blockers and their related drugs.