Spherical silica materials are the best performing supports for HPLC applications but they also are the most expensive. The IMPAQ® angular silica gel is the spherical alternative for preparative applications. IMPAQ® silica gels provide very efficient separations at much lower price. IMPAQ® is premium grade angular silica designed for High Performance Liquid Chromatography (HPLC) and other applications where consistent high purity and narrow distribution of pores and particle dimensions are required. It is the only non-spherical product performing successfully in large-scale HPLC applications. IMPAQ® is a fully porous gel in which the surface area, porosity and rigidity have been optimized for loading capacity and mechanical stability.
This cost efficient material has an irregular particle shape with smooth edges and a very narrow particle size distribution. The high specific surface area (500 m2/g for 60 Å pore size) allows the improvement of loading capacities for reversed-phases.
For irregular support, the average diameter is calculated by defining an equivalent average spherical diameter. From the following scanning electron microscopy (SEM) picture, it is easy to see the tight particle size distribution of this material, which is much better than standard silica and comes close to spherical silica. The graph presented on the next page shows two Microtrac analysis of a 10 µm IMPAQ® silica gel synthesized in 2002 and another one synthesized in 2004. It is easy to appreciate the batch-to-batch reproducibility of the synthetic method.
By carefully controlling the particle size of the silica precursor prior to the condensation we are able to greatly improve the robustness of the finished product. After the grinding and sieving steps are performed, there are extra steps to smooth out the edges to make the product pressure tolerant for HPLC applications. Fine particles generation is thus greatly reduced.