Enantioresolution of three β-blockers using L-glutamic acid as chiral selector by thin-layer chromatographic methods

Stereoselective dependence of active pharmaceutical ingredients for their pharmacokinetics inspired the researchers to develop new analytical methods for enantiomeric separation to enhance drug therapeutics. Enantiomeric separation of three beta-blockers, namely, (RS)-pindolol, (RS)-alprenolol, and (RS)-sotalol has been achieved by direct thin-layer chromatographic approaches involving L-glutamic acid (L-Glu) as chiral selector. Three different approaches adopted were as follows: (i) chiral thin-layer plates were prepared by adding L-Glu in the silica gel slurry, (ii) mobile phase and stationary phases were achiral where chiral auxiliary was pre-mixed with active pharmaceutical ingredients solution in the specific ratio (1:3), and (iii) L-Glu was mixed in the mobile phase and plain plates without L-Glu were used. Several combinations of solvents were thriving in three different approaches for the enantioresolution of three pharmaceuticals. After optimizing successful resolution, spots of corresponding isomers were located using iodine as a detecting agent. The detection limits for each enantiomer were reported to be between 1.3 and 1.7 mu g spot(-1).