Construction of large-volume monolithic columns.

Monolithic supports have become the subject of extensive study in the past years. Despite their advantageous features and many successful chromatographic applications in the analytical scale, only a very few examples of larger volume monoliths were described. In the case of GMA-EDMA monoliths, this can be attributed to the fact that due to the exothermic polymerization a pronounced temperature increase inside the monolith significantly affects the structure. The temperature increase depends on the thickness of the monolith, and consequently, there is an upper limit that allows the preparation of a unit with a uniform structure. In the present work, we have analyzed a heat release during the polymerization and have derived a mathematical model for the prediction of the maximal thickness of the monolithic annulus having a uniform structure. On the basis of the calculations, two annuluses of different diameters were polymerized and merged into a single monolithic unit with a volume of 80 mL. In addition, a special housing was designed to provide a uniform flow distribution in the radial direction over the entire monolith bed. It was shown that such a monolithic column exhibits flow-independent separation efficiency and dynamic binding capacity up to flow rates higher than 100 mL/min. The separation and loading times are in the range of a few minutes. The pressure drop on the column is linearly dependent on the flow rate and does not exceed 2.5 MPa at a flow rate of 250 ml/min.