Direct high-performance liquid chromatographic separations of metoprolol analogues on a Chiralcel OD column using chemometrics

Abstract

The chromatographic behaviour of sixteen racemic amino alcohols was studied under normal-phase liquid chromatography conditions using Chiralcel OD as the chiral stationary phase. The use of addition of water to the mobile phase sped up the equilibration time of the chromatographic system. The influence of content of mobile phase 2-propanol, water and acetic acid on enantioselective retention was investigated using a statistical factorial experimental design and the experimental results were evaluated using multivariate analyses. The impact of small changes in chemical structure of the tested amino alcohols on enantioseparation was also investigated in order to give some insight into the chiral recognition mechanism. The structure of the amino alcohols differ in distance between the chiral centre and the nitrogen atom, type and position of substituents in the aromatic ring and type of substituent attached to the nitrogen atom. Appropriate concentrations of water and acetic acid in the mobile phase made it possible to control the elution order of the enantiomers of an analogue to metoprolol. The high enantioselectivity obtained for several of the tested amines makes it possible to determine enantiomeric purity even if the main peak elutes before the minor enantiomeric impurity peak.