Octadecylamine dendrimers modified silica for novel mixed-mode liquid chromatographic stationary phases

Two novel octadecylamine dendritic stationary phases, called Sil-G1-AS and Sil-G2-AS, were innovatively prepared by grafting ethylenediamine and 1,4-butanediol diglycidyl ether (BDDE) onto silica surface, followed by octadecylamine (AS), and further used for mixed-mode chromatography (MMC). The prepared materials and intermediates were characterized using Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), contact angle analysis and thermogravimetric analysis (TGA). The chromatographic behavior of Sil-G1-AS and Sil-G2-AS columns was investigated using compounds of phenols, alkylbenzenes , nucleosides , polycyclic aromatic hydrocarbons (PAHs), vitamins, alkaloids, anilines, aromatic acids and flavonoids . The prepared stationary phases exhibited MMC behavior of reversed-phase liquid chromatography (RPLC), ion exchange chromatography (IEC) and hydrophilic interaction chromatography (HILIC) under different mobile phase conditions. Among them, Sil-G2-AS stationary phase has stronger hydrophilic properties and performs better chromatographic performance in HILIC, while Sil-G1-AS has stronger hydrophobicity . In addition, the stability of the two chromatographic columns was further investigated. These results demonstrated that Sil-G1-AS and Sil-G2-AS columns can provide multiple retention modes for the separation of a wide range of analytes with excellent stability.