Monolithic stationary phases preparation for use in chromatographic and electromigration techniques: The state-of-the-art

Over three decades, monolithic stationary phases have attracted expressive attention in separation science, especially for liquid chromatography and capillary electrochromatography. Monolithic columns can be constituted by in situ polymerization or consolidation of inorganic, organic or a hybrid of both classes of these substances forming a continuous porous bed inside of a separation tube. Several parameters involved in monoliths bed synthesis, including the nature of the monomers, combination of porogenic solvents, types of possible processes and reactions, can be adjusted, modified and optimized, affecting its morphology, pore structure and chromatographic performance. In this context, this work aims to briefly discuss the steps involved in the monolithic columns production, including advances in the preparation of precursor solution, tubing pretreatment and solution introduction, in situ reaction and posttreatment of the column. Some particularities of the main classes of monolith compositions are also summarized, highlighting some associated historical landmarks and analytical applications. Different types of processes and reactions, which may include sol-gel, polycondensation, free radical polymerization and click reactions are described. Finally, this work is expected to encourage and help researchers to find and produce a suitable monolith for use in the analytical separation area.