Resolution of the enantiomers of racemic atenolol, metoprolol, propranolol, and labetalol, commonly used β-blockers, has been achieved by TLC on silica gel plates using vancomycin as chiral impregnating reagent or as chiral mobile phase additive. With vancomycin as impregnating agent, successful resolution of the enantiomers of atenolol, metoprolol, propranolol, and labetalol was achieved by use of the mobile phases acetonitrile-methanol-waterdichloromethane 7:1:1:1 (v/v), acetonitrile-methanol-water 6:1:1 (v/v), acetonitrile-methanol-water-dichloromethane-glacial acetic acid 7:1:1:1:0.5 (v/v), and acetonitrile-methanol-water 15:1:1 (v/v), respectively. With vancomycin as mobile phase additive, successful resolution of the enantiomers of metoprolol, propranolol, and labetalol was achieved by use of the mobile phases acetonitrilemethanol-0.56 mM aqueous vancomycin (pH 5.5) 6:1:1 (v/v), acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5) 15:1:2 (v/v), and acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5)-dichloromethane 9:1:1.5:1 (v/v), respectively. Spots were detected by use of iodine vapor. The detection limits were 1.3, 1.2, 1.5, and 1.4 μg for each enantiomer of atenolol, metoprolol, propranolol, and labetalol, respectively.
