Polyethyleneimine Immobilized on Silica Endcapped with Octadecyl Groups as a Stationary Phase for RP-LC

摘要

A new reversed stationary phase was prepared, based on thermal immobilization of trimethoxysilylpropyl modified polyethyleneimine onto silica particles endcapped with octadecyl molecules. The physicochemical and morphological properties of the stationary phase were characterized by solid state cross-polarization and magic angle spinning ~(29)Si nuclear magnetic resonance, infrared spectroscopy, porosimetry, and elemental analysis. For the studies on reversed phase high-performance liquid chromatography (HPLC) retention, separation of the established Tanaka and Engelhardt test mixtures was performed. The stationary phase showed a typical partition mechanism for the reversed phase; however, the low hydrophobicity required a low organic content solvent in the mobile phase for chromatographic separation of more hydrophobic compounds. The stationary phase also showed low residual silanol activity for the elution of basic compounds due to the protection offered by octadecyl endcapped molecules and the competition provided by the imine groups of the polymeric layer. The proposed stationary phase possesses interesting selectivity and is convenient for applications requiring the separation of more retentive compounds in conventional HPLC columns using more aqueous mobile phases.