Chiral separation of beta-adrenergic antagonists, profen non-steroidal anti-inflammatory drugs and chlorophenoxypropionic acid herbicides using teicoplanin as the chiral selector in capillary liquid chromatography

Abstract

Three groups of structurally diverse chiral compounds were used to study the interaction mechanism responsible for stereoselective recognition with teicoplanin as chiral selector in capillary liquid chromatography. Teicoplanin-based chiral stationary phase (CSP) was used. The effect of the variation of mobile phase composition on retention and enantioselective separation was studied. The mobile phase composition suitable for enantioresolution of the various chiral compounds differed according to the interaction forces needed for chiral recognition. Mobile phases with high buffer portion (70–90 vol.%) were preferred for separation of enantiomers of profen non-steroidal anti-inflammatory drugs and chlorophenoxypropionic acid herbicides that require hydrophobic interactions, inclusion and π–π interactions for stereoselective recognition with teicoplanin. Higher concentration triethylamine in the buffer (0.5–1.0%) increased resolution of these acids. On the other hand, H-bonding and electrostatic interactions are important in stereoselective interaction mechanism of β-adrenergic antagonists with teicoplanin. These interaction types predominate in the reversed phase separation mode with high organic modifier content (95% methanol) and in polar organic mobile phases. For this reason β-adrenergic antagonists were best enantioresolved in the polar organic mode. The mobile phase composed of methanol/acetic acid/triethylamine, 100/0.01/0.01 (v/v/v), provided enantioresolution values of all the studied β-adrenergic antagonists in the range 1.1–1.9. Addition of teicoplanin to the mobile phase, which was suitable for enantioseparation of certain compounds on the CSP, was also investigated. This system was used to dispose of nonstereoselective interactions of analytes with silica gel support that often participate in the interaction with CSPs. Very low concentration of teicoplanin in the mobile phase (0.1 mM) resulted in enantioselective separation of 2,2- and 2,4-chlorophenoxypropionic acids.