Optimized enantioselective separation of clenbuterol on macrocyclic antibiotic teicoplanin chiral stationary phase

An isocratic and simple high performance liquid chromatographic method was developed for the direct resolution of clenbuterol enantiomers. The method involved the use of the macrocyclic antibiotic teicoplanin chiral stationary phase column known as Chirobiotic T. Several mobile phase compositions were studied to optimize the resolution of racemic clenbuterol. The role of using different solvents, e.g. methanol, ethanol, and acetonitrile as organic modifiers and the effect of triethylamine and acetic acid on the enantioseparation of clenbuterol were investigated. The best base-line separation was achieved using mobile phase consisting of ethanol containing 0.3% acetic acid and 0.2% triethylamine where the stereochemical separation factor (alpha) obtained was 1.58 and the stereochemical resolution factor (R-s) was 1.48. Under these chromatographic conditions, the (-)-R-clenbuterol eluted first with a capacity factor k(1)', of 1.89 followed by the (+)-S-enantiomer with a capacity factor of k(2)', of 2.99.