Preface


High-performance liquid chromatography has become the predominant global tech- nology over the past four decades. The major reason for the rapid growth of this technique has been the evolution of packing materials used to affect the separations. The traditional packing materials have been particulates. However, the recent develop- ment of an alternative column packing material – a one-piece porous solid known as a ‘monolith’ – has transformed the field. Monolithic stationary phases and columns have rapidly become highly popular in liquid chromatography, although they are relative youngsters in the realm of commercial separation columns. Traditional packed-column chromatography is a mature technology and can be


described as follows: during a chromatography run, a pump is used to push a mobile phase through a packed column. The liquid can go freely through the voids but meets certain resistance when permeating the interior of the porous packing materials. When a liquid sample is injected into the column, the analyte molecules will diffuse differently back and forth between these two regions, which affects the column’s ability to thoroughly separate analytes with similar properties. Large biomolecules such as proteins are especially affected due to their slow diffusion rates. Chromatographers have worked hard to solve this problem by reducing particle


sizes to shorten the distances between the pores of which the molecules diffuse in and out. The introduction of ultra performance liquid chromatography and ultra high- performance liquid chromatography is a good example. By using smaller particles, the peak capacity (number of peaks resolved per unit of time) can be significantly extended to new limits, which can take full advantage of chromatographic principles to run separations using shorter columns and/or higher flow rates with superior resolution and sensitivity. The reduction in the size of the voids led to lower column permeability, which


caused mobile phases to move slowly unless high-pressure pumps were used to increase the flow. However, the use of high pressure presented technical challenges and it destroyed some types of columns. Therefore, the development of high-pressure pumps was not always a good option. At this time, monolithic packing materials were developed and they have acquired extensive applications during the past decade. The development of monolithic columns has followed a track opposite to that of conven- tional HPLC columns, for which separation occurs as molecules diffuse in and out of the pores on the surface of the particles and the driving force for the separation is


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