CONICET | Buscador de Institutos y Recursos Humanos

The optimization of a given separation in liquid chromatography includes the reduction in analysis time. Since early times, it has been known that a decrease in the particle diameter of packed columns improves the separation efficiency. Thus, it is possible to reduce the column length and, consequently, decrease the run time. However, there is an instrumental limit in the reduction of particle diameter set by the pressure drops that can withstand the pumps to supply a fluid at a reasonable flow-rate. Recently, a new design of pumps was developed which can be operated up to 800-1000 bar, i. e., the instrument is capable to generate relatively high flow rates with particles below 2 mm. Ultra Fast Liquid Chromatography (UFLC) was coined to refer to liquid chromatographic experiments under these experimental conditions. Besides the instrumental requirements, which imply very high costs, another disadvantage of working with such small filling particles is that the column can easily be blocked, thereby reducing its lifetime. The development of monolithic materials introduced new possibilities. The large permeability of these monolithic beds allows set relatively high flow rates without a significant increase of pressure. Furthermore, if the column temperature is increased in order to reduce the eluent viscosity, an even more favorable experimental condition results in order to reduce the analysis time. That is, high flow rates and relatively high temperatures, using nonconventional monolithic materials with conventional instruments can be conceived. In this work we studied the separation of two families of pharmaceutical compounds: non-steroidal anti-inflammatory drugs (profens) and b-blockers, in a reversed-phase octadecylsilica monolithic column, using acetonitrile/buffer mixtures as mobile phases under isocratic conditions at high temperatures and high flow-rates. We critically compared the results obtained under these conditions with those obtained with conventional columns packed with particulated materials. Resolution of critical pairs, peak symmetries, isocratic analysis time and pressure drops are discussed.