Multicomponent Ugi reaction as a tool for fast and easy preparation of stationary phases for hydrophilic interaction liquid chromatography. Part I: The influence of attachment and spacing of the functional ligand obtained via the Ugi reaction

Abstract

A number of novel stationary phases for hydrophilic interaction liquid chromatography (HILIC) containing both amides and hydroxyl groups in the functional ligand were obtained by the multicomponent Ugi reaction on the aminated silica surface. The ligands were either attached directly to the substrate surface or spaced by 1,4-butanediol diglycidyl ether (1,4-BDDGE) as a linker. Chromatographic parameters of the obtained stationary phases were evaluated using Tanaka test and model mixtures of sugars, amino acids, and water-soluble vitamins. The adsorbent obtained by direct substrate modification by the Ugi reaction showed the increase of hydrophilicity according to the Tanaka test and high selectivity toward all the analytes with separation efficiency of up to 40000 N/m. The separation of 9 sugars in 12 min, 7 amino acids in less than 18 min, and 7 vitamins in less than 10 min with only 10 cm long column was provided. The effect of introducing 1,4-BDDGE as a linker between the substrate surface and the ligand formed via the Ugi reaction was demonstrated and discussed.