The preparation of a poly (pentaerythritol tetraglycidyl ether-co-poly ethylene imine) organic monolithic capillary column and its application in hydrophilic interaction chromatography for polar molecules

An easy single-step thermal treatment “one-pot” approach for the preparation of poly (pentaerythritol tetraglycidyl ether-co-poly ethylene imine) organic monolithic capillary columns was developed successfully. The column was prepared by the epoxy-amine ring-opening polymerization of pentaerythritol tetraglycidyl ether (PTE) with poly (ethylene imine) (PEI) using acetonitrile (ACN) and polyethylene glycol 600 (PEG 600) as the porogenic system at 60 °C for 12 h. The obtained monolith was homogeneous and permeable. It achieved the high-efficiency separation of polar molecules including amides, nucleosides, bases, phenols, and benzoic acids in capillary liquid chromatography (cLC). The highest column efficiency reached ca. 101,000 plates/m (for guanine) on monolith poly(PTE-co-PEI) at 0.64 mm/s, and satisfactory chromatographic performance with column efficiencies ranged from 45,500 to 97,000 plates/m was achieved for the four amides. A typical hydrophilic interaction liquid chromatography (HILIC) retention mechanism was observed with high organic solvent contents (>60% ACN). Also, the polymer-based monolithic column was successfully applied to separate the tumor markers. Furthermore, the poly(PTE-co-PEI) monolith could be easily modified with 1, 2-epoxydodecane, which reacted with the amino groups presented on the surface of the poly(PTE-co-PEI) monolith. Hydrophobic interactions were observed during the separation of alkylbenzenes and anilines on the post-modified poly(PTE-co-PEI) monolith. Together, these results confirm the feasibility of the epoxy-amine ring-opening polymerization reaction during the fabrication of a monolithic column with high efficiency for cLC applications.