Synthesis and applications of BEH particles in liquid chromatography

Ethylene-bridged hybrid inorganic–organic (BEH) particle technology has allowed for the improvement in separation performance for a range of separation modes, including reversed-phase, hydrophilic interaction and size-exclusion chromatography. In this report, the process of preparing BEH particles, the characterization of these materials and their use for unique chromatographic applications are explored.

The development of column packing materials is a competitive field that is the focus of many industrial research and development (R&D) groups worldwide. The result of these efforts is the commercialization each year of new families of separation columns — all claiming to have improvements over the prior technologies. End users may wonder why we need so many different column brands and phases.

Figure 1: Understanding how to optimize research parameters to meet user needs is a critical factor in the development of new chromatographic materials.
The question asked in an industrial R&D setting is: How can a new family of column packings be differentiated from others in the marketplace? To achieve a successful product, R&D efforts need to be focused on user needs. As shown in Figure 1, there are a number of user considerations for new separation columns. A new column family may try to differentiate on one or more of these user needs.

Because user needs change over time, it is critical for an R&D team to be able to feel the pulse of these changing requirements. In the 1990s, users were struggling with column reproducibility and as a result, industrial R&D efforts focused on improving the reproducibility and purity of porous silica packing materials (1). At the turn of the century, a major user need was increased selectivity options and research groups addressed that need with the development of new stationary phases (2).

Our exploration of hybrid inorganic–organic materials (denoted hybrids) started in the mid-1990s as a way to address the needs of scientists using reversed-phase chromatography for improved selectivity, efficiency, resolution, peak shape, stability and reproducibility (3). We found hybrid particles to be high performance materials that are well suited to meet these needs. This technology has expanded into the preparation of new materials to address user requirements in hydrophilic interaction (HILIC) and size-exclusion chromatography (SEC). In the following sections, we will detail how hybrid particles are prepared and how their unique qualities can be used to improve separations.