Monolithic Columns: The New Era in the Analysis of Organic Compounds by Liquid Chromatographic Techniques

The increasing demand for ultra-fast separations has motivated the development of new materials in the field of chromatographic stationary phases. Since High Performance Liquid Chromatography is a powerful and popular technique, the importance of improving existing supports, as well as the development of new types of columns is more than profound. The advent of monolithic columns offered new practical possibilities for decreasing retention times and/or increasing column efficiencies, while pressure restriction was significantly eliminated. Monolithic columns are prepared by means of a polymerization process from either organic polymers, such as polymethacrylates, polystyrenes or from inorganic polymers, such as silica. Highly porous rods of silica with a bimodal pore structure consist of macropores and mesopores. The former consist of a dense network of pores, while the latter form contain fine porous structure of the column. This structure dictates the major chromatographic features of monolithic columns. Since many analytical methods employing conventional columns already exist, it is very challenging to study their transfer at similar or higher flow rates using monolithic rods with a considerable gain in time. Applications of analytical methods in organic analysis employing monoliths as stationary phase include pharmaceuticals, biofluids, food matrices, environmental samples, biochemical species, proteomics etc. Several additional application modes of monolithic columns have been explored. An emergence of applications is expected to continue as long as more experience is gained with monolithic column technology. Such an attempt has been prompted also by the need of reduction in organic solvent consumption, in the frame of environmental friendly methods.