![]() Several core–shell type sorbents (also called pellicular sorbents) were commercialized in the late 1970s. Therefore, at the time of these advancements (and arguably even today) core–shell type sorbents offered an ideal compromise between the capabilities of silica manufacturing technology and those of the existing liquid chromatographic systems.įigure 1 - SEM and TEM images of Halo® ( Advanced Material Technologies, Wilmington, DE) (left) and Kinetex ® ( Phenomenex, Torrance, CA) (right) particles. However, the capabilities of both silica manufacturing and LC systems lagged behind the requirements imposed by smaller particles. While in the late 1960s and early 1970s the most commonly used sorbent for LC was 10–50 μm irregularly shaped silica, spherical 10-μm particles were developed in the mid-1970s 5-μm spherical particles were developed in the ’80s. At the time of these early innovations, it was well understood that higher performance in LC could be achieved with the use of smaller particles. The primary drivers for investigating core–shell type sorbents for LC were improving speed while maintaining or improving performance. One of the preferred inorganic substances used to prepare the superficially porous sorbents was silica, which made further chemical modification of the pore surface, e.g., with C18, relatively straightforward. 2 The network of spaces between the fused nanoparticles formed the chromatographically active pore volume. Kirkland prepared what he called superficially porous sorbents by successively fusing layers of nanometer-sized nonporous inorganic spherical particles (or nanoparticles) to a 10-μm nonporous solid spherical core. The major drawbacks of the pellicular sorbents were 1) very limited surface area manifesting itself as low retention and sample loading capacity, and 2) poor uniformity and mechanical stability of the porous layer. 1 This layer served as the chromatographically active surface via chemical modifications such as cation and anion exchange functionalities. One of the earliest examples of this concept was the pellicular, or thin-skin, sorbents prepared by Horváth and Lipinski in the late 1960s, consisting of 30–50 μm, nonporous, solid glass spheres coated with a 1–2 μm thick layer of porous organic polymer. The concept of superficially porous or, as they are now commonly referred to, core–shell, HPLC sorbents was first introduced over 50 years ago. ![]() Considerations for choosing a core–shell column will be given as well. This article discusses the advantages and history of core–shell particle development. A chromatographic column packed with core–shell particles offers several significant advantages over columns packed with fully porous sub-2-μm particles. Since the introduction of ultrahigh-performance liquid chromatography (UHPLC) in 2004, one of the most significant technological advancements has been the introduction of core–shell columns.
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