Two new azamacrocycle-based stationary phases for high-performance liquid chromatography: Preparation and comparative evaluation

In this paper, two new azamacrocycle-bonded stationary phases for high-performance liquid chromatography are described. The new phases were prepared by respectively coupling a 14-membered Curtis macrocycle and a 30-membered hexaazaannulene to γ-chloropropyltrimethoxylsilane-modified silica and characterized by elemental analysis and infrared spectroscopy. To understand the effects of the structures of the azamacrocyles and their functional groups upon the retention and separation, the chromatographic behaviors of the two stationary phases were compared by eluting alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs) and aromatic amines. The two new phases demonstrated unique selectivity and fine chromatographic performance, which were guaranteed by multiple interactions, including hydrophobic, hydrogen-bonding, π–π and dipole-induced dipole interactions between stationary phase and solutes. On the other hand, the difference between the structures of embedded azamacrocyles did lead to remarkable dissimilarity in the shape and planarity recognition of isomers, which was highlighted by the 30-membered hexaazaannulene-bonded phases’ superiority over 14-membered tetraazamacrocycle-bonded phases’ in discriminating specific PAHs. With a wide range of probes, the linear solvation energy relationship model was also applied to evaluate the chromatographic properties of the two stationary phases, further verifying the chromatographic results.