New silica gel-based monolithic column for nano-liquid chromatography, used in the HILIC mode

This paper describes the synthesis and chromatographic and morphologic characterization of two monolithic silica nano-columns (50 µm i.d.) prepared by sol-gel processes, using hydrophilic interaction (HILIC) mode separations to evaluate their performance. Two types of monoliths were prepared by varying the precursors (tetraethoxysilane or a tetraethoxysilane-methyltrimethoxysilane mixture) and by changing the type of catalyst (urea and acetic acid or ammonium hydroxide). The monoliths were characterized by scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy and nitrogen adsorption-desorption isotherms. The columns were tested for the separation of several mixtures, with the organically modified silica (ormosil) column successfully separating two challenging mixtures using HILIC conditions.