Preparation And Evaluation Of Macrocyclic Polyamine-based HPLC Stationary Phase

This paper described the syntheses of three azamacrocycles and their finechromatographic behaviors when applied for the preparation of stationary phases forhigh performance liquid chromatography （HPLC） with an aim to extensively andprofoundly explore the employment of azamacrocycles in HPLC stationary phase andcorresponding chromatographic mechanism and to deepen the understanding of themultifunctional properties of azamacrocycle involved in the liquid chromatographicseparation process.Through the condensation of diaminoethane with acetone and benzalacetonerespectively and subsequent reduction of imine intermediates, twotetraazamacrocycles, namely5,7,712,14,14-hexamethyl-1,4,8,11-tetraazacyclotetrade-cane （Me₆[14]aneN4） and5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetrade-cane （Me₂Ph₂[14]aneN₄） were obtained; through the same procedure oftrans-1,2-diaminocyclohexane with terephthaldehyde, a hexaazamacrocycle, i.e.1,4,11,14,21,21-hexaaza-（2,3:12,13:22,23）-tributano-（6,9:16,19:26,29）-trietheno-（1H,2H,3H,4H,5H,10H,11H,12H,13H,14H,15H,20H,21H,22H,23H,24H,25H,30H）-octadecahydro-（30）-annulene （cycHe₃Ph₃[30]aneN₆） obtained. These three azamacrocycleswere characterized by IR, NMR and MS. Then the macrocycles were covalentlybonded to silica using γ-chloropropyltrimethoxylsilane as coupling agent. Thestructures of resulted material, v.z. Me₆[14]aneN₄CPS, Me₂Ph₂[14]aneN4CPS andcycHe₃Ph₃[30]aneN₆CPS, were characterized by elemental analysis and IR.With32solutes including aromatic and aliphatic compounds, the linear solvationenergy relationship （LSER） method was successfully used to chromatographicallyevaluate the new phases in reversed phase mode in a quantitative manner. Theanalytes including non-polar and polar ones, such as alkylbenzene, organic pesticides,phenolic compounds, aromatic amines, polycyclic aromatic hydrocarbons （PAHs） aswell as Vitamin E, all of which contained greatly diversified functional groups, wereused to assess the chromatographic properties of the new stationary phases. The results demonstrated that the azamacrocycle-bonded stationary phases possessedevident hydrophobic characteristics, and additionally that π-π, dipole-dipole andhydrogen bonding interactions plus acid-base equilibrium could also besimultaneously offered by these new stationary phases, as a result of which excellentchromatographic performances were guaranteed. Comparison between the stationaryphases clarified that the azamacrocycle-bonded phases were suitable for separation ofpolar analytes, even outperformed the ODS phases when separating aromatic aminesand phenols. It was noteworthy that the cycHe₃Ph₃[30]aneN6CPS excelled the restmacrocycle-bonded phases in most separation cases by exhibiting superior selectivityand remarkable retention capabilities, which were presumably due to the stronger π-πstacking and shape recognition resulting from its more rigid structure and largercavity.Hopefully, these promising new stationary phases will expand the scope ofmultifunctional retention properties and prompt the development of universallyapplicable separation material.